When I made this latest discovery, in the glory-hole under the stairs, I immediately thought of offering it to the Blipfoto rescue initiative. Since then the communication from Joe has raised our spirits and given us some hope that Blipfoto will live. Hooray!
On reflection this 10x8 inch box seems very small for medical supplies for a 4-man tank crew. I discovered that it would have contained, apart from bandages, mainly chloroform and morphine. The Old Man was in the Rifle Brigade rather than an armoured division but this piece of equipment definitely dates from WW2.
Edit: See below what Bookworm1962 says about the joint role of the Rifle Brigade and the Armoured Divisions.