Historical Background and Review of the German Mercator Knife (aka "Cat Knife") 

I've had one for 58 years, it's lost the black coating but still a great knife, true German quality.

I have my stained, well used one in my back pocket right now... I've carried it for many years. Mine's a veteran of many days at work, hiking, & camping, and is pretty much always in my pocket or car glove box. Simple & ultra reliable given a bit of sharpening & a drop of oil. A light tap with a peen hammer on the pivot rivet closes any play in the blade that might develop over the years....

Ich habe mir die Geschichte dieses Messers vor einigen tagen bereits zu Gemüte geführt. Ein wirklich interessantes Stück deutscher Messergeschichte. Danke für die Vertiefung meines Wissens über dieses Messer. Ich werde es definitiv auf meine zukünftige Liste setzen. Beste Grüße, Chris

Welch glücklicher Zufall auf dieses Video zu stoßen. Profundes Wissen klar dargeboten. Perfekt. DANKE!

Awesome everyday utility knife. I am a New Zealand construction worker and use it almost daily for jobs where the Tajima etc segment knives would simply snap. Easy to sharpen and you can be rough as hell with it. Always gets a few eyebrows raised and some curiosity when I pull it out too. Makes a fantastic Christmas present for any nephews as well. Recommend.

Fantastic explanation and history of this knife. When I was a child I remember huge fuss and the police searching the grounds of my primary school because a 'Black Cat Knife' was found lying near the football field and for weeks parents were talking about teenagers getting more dangerous and like American gangs, and anti-social activity. Punk rock music got the blame, of course. I was always wondering what exactly a Black Cat knife was, but assumed it was just slang, until I came across your superbly executed and interesting video here completely by random.

Mercator is also the map projection most of us use on our maps. Maybe herr Kaufmann was alluding to the point that his tools were also sold across the world?

A video as timeless as the knife it was made about. Amazing job.

Qualität setzt sich durch. Danke für die, wie immer, gute Recherche.

Das war eine ausgezeichnete Video, mein Herr! I was very impressed with the amount of detail you put into this video when you talked about the knife's history (its original manufacturer, alternative names, English translations for German words, history of production, etc). I can't tell you how many knife reviews I see on RU-vid where guys buy a knife and know next to nothing about it when they decide to do an online review. You obviously have your stuff together. Gute Arbeit!

Thanks for video...nice job!! I just bought a Black Cat and it's nice to know the history. Very unique knife!!

Thanks for the excellent video. I had one of these as a kid in New York in the '70s and just rediscovered them. Had no idea of the history behind them until now. We just called them "Cat Knives" as you say. They were street legal in NYC and their flatness made them easy to carry. Really great knife with a good edge. I thought they had vanished decades ago and it is really cool to see they are still around!

They are great knifes; my dad passed his one down to me! It is my favorite knife, here in New Zealand!

Thank you Stefan for a wonderful and professional educational video! Done as only a German could do! The K55 knife is a very dear and old friend to me. I started carrying one in 1963, which I bought brand new in New York City where I lived. One day I needed to use the knife while I was trapped at the end of a subway station as a very scary man eyed and approached me. I pulled out the knife and just held it out....shaking with fear...He saw the knife and walked away. I still have that knife.

I prefer the carbon steel too. I have a personal history with this knife. It’s one of the best knives I’ve ever owned and EDC’d that knife for many years. I after around 25 years of heavy use, I finally broke the blade in half while using it with a ball peen hammer as a wood chisel. With the tip gone, it still works as a wood chisel. After snapping my first one on half (through abuse), I immediately bought another one. I hope to always own at least one of these. They really are outstanding and underrated.

I have my Black Cat knife for well over a good year now and it’s one of my favorite pocket knifes. I bought it based on your review which IMO is the best on RU-vid it’s funny a lot of people mention you so I hope you take it as a complaint to your research. Thanks from Colorado USA.

Best pocket/utility knife ever made!

Thank you for sharing the history behind this iconic cool little knife.

Excellent video. I wish every You Tube video was so well put together. Thank you for spending the time to do the video.

I just ordered this knife today. Nice video , thanks for sharing.

Thanks for this interesting and informative review. I have just sent for one, and look forward to using it. I am sure that when I was a boy (I am a pensioner now) my Mum used to have one of these, which her Dad brought back from the 1914-1918 War, in which he fought. It is unfortunate that it has disappeared over the years, as I would like to compare one that is 100+ years old with it's 21st century counterpart.

Great video! You have a very pleasant presentation style, and clear narration. Here in the US, these knives were a staple of military surplus stores. Even in the 1980s and 90s, such stores were selling new production Otto Mercators and marketing them as "genuine Nazi fighting knifes!" which was a hilarious claim. They would also sell new Opinel knives marketed as "French Resitance combat knives" or "Legionaire folding knives."

Wunderbar! I was interested and you sold me on the history! Greetings from southern California

Informative and well done video. I love this knife, I have used one as my EDC for about a year. After putting it through pretty hard use, the blade play is less than I would have expected in such a well priced knife. As in the video, I also keep my carbon steel K55 sharp with a Spyderco Sharpmaker. I figured out how to open it one handed, which has made it nudge out my other one handers. It is fun to have and hold a piece of history and be able to share it with others. Thanks Stefan!

I found one in my garage once, all rusted over and I had thought it was buggered. Just playing around with it though it opened easy enough and after a quick wipe down I found it was still sharp!

A great Solution as EDC - Tool . I love this part of German History and Story in his backround...! I mean its possible to hold this herritage when you use and collect one of this knives and explain this another people which interesting in Knives. Best Regards and take Care Stefan

thanks for the history, I own one of these knives. I bought mine back in the 70s and I now keep it on my desk for opening letters and packages.

Excellent video, as always, Mr. Schmalhaus. I wonder when an English version of your excellent book would be available. I have purchased the Mercator because of a video of yours and, since then, I am very happy with this knife. In fact, that is the only EDC knife that I carry for food prep -- peeling an orange with it is such a pleasure... And, as you say, its price was quite reasonable. Thank you for letting me know some of the history of such a dear to me blade.

I have several Mercator knives and knives of similar design . One thing i noticed that is helpful to date the knife to a period is the spacer in the back of the knife. the earlier knives both Mercator and the similar knives had a red spacer made of vulcanised fiber like that that was used for tp washers and gaskets. I also have one with two shims of plain steel. and it looks original. The other thing on the earlier knives is the wear that results in an almost triangular blade shape and there is also a gradual thining of the blade thickness from all the sharpening on an oil stone.. This wear could not be produced on a" fake" vintage knife. Sadly you see many knives that are obviously modern, listed on sites like eBay as WW1 or WW2 or my great grandfathers war memorabilia by conmen . The later knives had a red plastic spacer and I have seen some that have a red nylon spacer that is not so easily fractured. I have seen some knives that were repaired/modified with a filler made of aluminium and a couple with brass filler pieces . I would love to know more of the history of these wonderful knives. All the best.

The Mercator knife is a real classic that should be in every knife collection. While such an old design, it is still an excellent cutting tool. Good overview !

I just got one in the mail! It's a lot more sturdy than I thought it would be. Im very satisfied with this purchase. Thank you for the great review of the history and practical usage of this knife.

Danke! Excellent video! I just received mine today along with a douk douk knife and a no.8 Opinel carbone. I love the history of these knives. The looks, the feel and the history! Thank you for telling us about this knife! Going to watch how they are made now. Take care and be safe! Hope this corona 19 crap goes away soon. I’m in the medical field and we have been on our toes. It’s just starting to hit here in Oklahoma, USA.

After your comment on the Hubertus video, I decided to check out the Mercator as well! It's such an interesting history, I couldn't help but buy one with the classic "black cat" and one with the new Otter Messer otter!

Very well done. I enjoy learning about classic knife history.

I have had this knife for about 10 years and have only been able to wonder about it's history. Thank you so much for making this video. I have had such a great affection for this knife and it is my favorite,I carry it daily. Your video explaining it's history has only made me love it that much more. The professionalism that you put into your review is much appreciated! Thank you...all the way from the great State of Texas!

Hey Stefan, Thanks for the video. Lots of great info. Cheers, Duane

Your videos are always awesome.......another fine excample.

I have carried one for over 20 years. Even in kombat in Iraq 03-04.

That was excellent! I've always wondered about the cryptic "K55K" meaning. I always thought it was a military knife, and here it is revealed simply a useful pocketknife. Thanks for the enlightening information!!

Very informative. Great video.

Sehr gut erklährt, Herr Schmalhaus!

I love this knife and carry mine often. Some peoplke are amazed when they see me with it, knowing that I own Benchmades, Spydercos and Emersons but the Kat knife has taken a lot of abuse over the years and never let me down. You are right it does take a terrifying edge with a little work. Thank you for the excellent vid, you are one of the best knife reviewers on RU-vid.

OMG, is always a pleasure to see your reviews!!!

I honestly think these knifes are so cool. My first name is Mercator. (Mer-K-Ter) and my dad always try’s to collect things that has my name or teach me things about my name. Thank you for the video very good

I recently got one and the factory sharpness is impressive.

Stefan, Thanks for another GREAT review!! I REALLY like the way that you add some history and background to your videos. Normally this wouldn't be the style of knife that I would buy, but now that I know the history behind it I just ordered one!

Great video! Thank you for making it. I had one of these knives as a child and loved it.

Stellar video! Your English is admirable. I own this knife, and it proudly stands with my pricey folders...

great review, beautiful knife

Your videos are truly a pleasure to watch. This knife has a very interesting history, thank you so much for another great review.

Aha, so now I know the history of my new knife. VOSS Cutlery Co., German design. Same blade except mine has a bone handle. I use a 6'' steel from Solingen Germany to sharpen. Great knife design. It replaces my Buck 110 and Ontario RAT1 because it has features from both of those knives that I like. The Buck has lock back but it's too heavy and I do not like a pocket clip on the other knife so this German knife design is just perfect for my EDC. Thank you for the great history lesson and take care from Canada.

That was facinating and very well done. Thank you.

Excellent description! Thank you!

Thank you for your very interesting historical research.

Excellent! Outstanding historical information on a great messer! Danke!

I have one myself and I like it very much. Great history! Thanks for sharing.

@sweetdaddyroses I script my videos, this helps me to avoid the "ums" and "uhs". I usually don't like videos where people turn on the camera and start talking without knowing where they want to end up.

Wow, what a story! Thanks for sharing your personal memories and experiences - even if it was a scary one.

Awesome review as always Stefan! You always know how to make everything flow together. Keep up the great work my friend.

I have an exact copy made in Pakiistan which is just as old as the ones in world war one. I have only sharpened it once, and it is still razor sharp. The lanyard ring on mine is ornate and very artistically done. They were very ahead of their time, and no modern knives today are so undetectable while riding in your pocket, as it is very flat, just like this earth.. Steel makes a wonderful liner, such as is just now being replaced by titanium.

I have it and it is a very good work man's knife.

Really good work!!

I found one at a UK surplus shop here in the Philippines... I was vlogging when I found it. I will post it soon :) More power sir!

As always very interesting history and knife knowledge!!! Greetings and love from the Netherlands!

reminds me of the douk douk with the folded metal handle and the bail.

Your video was so interesting and elightening that just for that I'm going to get that knife. Thanks for sharing all this.

Excellent introduction and a valuable history lesson. I think I'll order one purely for collectors' value :)

Another great, entertaining and informational video! Thank you very much! Gotta have one of these...

excellent video sir! thanks for the history. Very well done and informative

Sehr schön, sehr interessant! I´m amazed how the americans love all these german knives and stuff

Great video. Loved the information on a classic knife. Mine still makes into my EDC rotation.

I never realized it, but over the years I've had several versions of this knife, one in particular I carried for quite some time while hitch hiking around the western United States. I was always quite amused by police who would often take out a ruler to measure my knife then let me go when they found it to be quite legal. I'm surprised they never tested one for traces of blood even though the only blood they would have found would have been my own.

Hi Stefan, beautiful presentation. After watching your video I got keen interest in this knife. As I result, I ordered it from Heinnie Haynes today. 😎

Great video. This is next on my list!

Great review and history lesson. Thank you.

@mrmonkeyman50 It might appear that the locking lever would stick into your hand or unlock, but in a normal grip it's not an issue. Remember, it's only about 6mm or 1/4" thick, so you'll naturally tend to grip the knife primarily by squeezing the sides of the knife between your palm and fingertips.

Truly an amazing review!

Stefan that was a very interesting video :). You always go the extra mile during your reviews and actually tell us about the whole history of the knife :)!!! And back than no1 needed a locking fancy tactical knife like we have today, this was a true pocket knife with a nice style may i add :). Great review!!

I absolutely love your videos. I would like to hear your thoughts on the douk douk.

Interesting video! Love the history stories!

Otter Messer recently revived the Mercator Multi (blade, awl, can opener, corkscrew).

Great historical review on a great knife, well done

Do more of these videos they are very interesting,informative,different and all around awesome.Think you'll ever do a vid about the different slipjoint patterns,Shilin cutter,Higonokami or well other obscure-ish historical knives from around the world?

@edwyrd Thank you very much for your kind words!

@wcropp1 I agree, carbon steel is more authentic on this kind of knives. Thanks for watching!

I’m going to have to buy one of those

Really enjoyed this, well researched. Thanks and look forward to whatever video is coming next. :)

Very cool and thanks for the history, have a great day.

Cool looking knife.

Wow, thanks so much! I have always wondered about this knifes strange markings...!

awesome knife got mine for 25 bucks carbon steel from amazon along with a whole bunch of different mora knives

I've bought a brass handled one with a carbon blade. Very nice, I like it so much that it kicked my delica out of my pocket (besides work, where I need the one handed opening and especially the pocket clip)

Its beyond simple. Wonderbar....

Thank you very much for your kind words!

Extremely interesting!!!

Fantastic video. I mean your reviews are simply unmatched. Theyre at a whole other level man. The only thing that would make them better is if you made more! ;) Anyway, considering the average soldier (especially back then) spent more time living/surviving outdoors than anything else. I can see how in WWI this pocket knife, a sawback bayonet and an entrenching tool sharpened to double as a hatchet made the average German soldier very self efficient in the wilderness.

After owning several Douk-Douks, I wanted another classic to carry. I prefer locking knives, and being in the states its ok to carry. Ordered off BladeHQ for $27, no beating that. Love the look of it, hope it performs just as well.

Thank you for your kind words!

@mrmonkeyman50 Thank you! - As far as I know, today XC 75 is used for the carbon steel blades, and 1.4034 for the stainless steel blades. But I have no idea which steels Heinrich Kaufmann & Söhne used back in the late 19th and early 20th century.

@jimkressin Thank you very much for your kind words!