That Besson is tiny - it just has a more open wrap than your York and a slightly larger bore - compared to the .656" York. Both of those would be considerd 4/4 size instruments, with the York leaning to the smaller side.
I believe the york bore to be larger than that. I had conn 52J new wonder which was .695 bore and the york blows better than the new wonder and has a larger bore. I also had a york master (bohm/Meinl) and the 1916 york also blew much freer than the master. The 52J was what I would consider a smallish 4/4. The york master was extremely similar to a jupiter 387, but I think the jupiter is an improved over the york master as the 387s I have played better. Both York/Besson are 4/4 size, but the amount of brass used in the Besson and the thickness of the end caps plus the longer valves and compensating tubing make it considerably heavier than anything this side of a 20J and way heavier than my york. I did not say the besson was a 5/4 or 6/4, merely that it is really big and heavy. It is also very mellow, it does not change tone colors like the york does, and in the wrong hands, that would make it worse. The besson has a very consistent sound and tuning. The besson's bore is .720 and I imagine the york is similar. This is not a EEb york but a BBb one. The york is probably .710 to .720. and if you look, you'll see that it is a hp/lp model with the extra loops in the 3v and tuning slide, plus the fact the slides are pulled out to an indication. From what i gather it maybe a 701, but with the july 1910 patent date, I don't know. And I don't really care what the bore size. There are other tuba reviews on my channel including a real 5/4 chinese 191 schlock up. Was a nice horn, but I just didn't play it out of legit settings and I found the York could work well in legit so might as well get the money out of the wangfuba and sold it a while back. I would say it was about 90% of a 191 once the valve linkage had been changed, but at 1/4th the price.
Well there's one way to find out the bore.... why not measure it? It's not that you called one a 4/4 or 5/4, it's that you've labeled them as small, medium, and large. When, what you're actually looking at is how the instrument is wrapped - how open or closed it is.
