I’ve been working on my own version of this project and I’m having the same problem.
From what I can tell, it’s a square outline with the letters ‘U.S.’ on top and then two lines of smaller text underneath. The first line looks like it’s in italic and the last line looks like it’s in regular text and probably ends in a T:
There was an ‘Indian Jones Jungle Cruise’ a while ago at Disney and that ride had a version of the crate on it. Whilst it did have the stamp on the left like in ROTLA, I can’t find a decent photo of the crate with enough detail to make out the wording. This is the best I could find:
http://www.laughingplace.com/lp/lotion/pics/SS20080529-DLIndy/P7-0002.jpg
The crates shown in the warehouse in KOTCS don’t seem to have the same lettering:
I’ve been through hundreds of fonts and the closest I can find is this:
USAAF Stencil Font | dafont.com It needs some cleaning up and isn’t quite perfect but I think it will make a good enough base to work from. I think I will whip a vector image of the stencil, I’ll post that when I’m done so that anyone else who wants the ‘correct’ stencil won’t have to spent hours trawling through hundreds and hundreds of subtly different fonts
I’m also curious to know what people think about the lock. After the ‘top men’ nail the lid down we briefly see them lock it with a sort of padlock bolt with hasps and staples, but then we don’t see the lock or a hinge when we see the crate being wheeled away.