I also collect M2 boxes. Here in Philippines almost all M2s are in relic barn find condition and well used as tool boxes after the war. All the boxes I have are my restoration projects. The design of the lid can collect rain water and in time causes the cover to rust. M2 ammo boxes were only produced during WW2 but they made so many of them that they were be issued in the US until the 60s or later. So even though they were issued some time after WW2, for me all M2 boxes are WW2 ammo boxes. The bullet direction on the lid of the box tells you the direction you should face the box when loading to the gun. I use one of my M2 boxes as a diaper storage box for my baby hahaha.
It’s actually funny, I found one of these at a garage sale in the US (I’m a Brit like yourself), and it does actually have the “grenade pin” on the front. I stumbled across your video, trying to find out how to lock the front with said pin, and I still haven’t figured it out!
