old lockbox letters...

I have this old Government lock box I'd like to re-stencil in the original pattern.
anyone have any clue what exactly this box was used for?
"Handle with care delicate instrument chamber mk4" is all that I can read for sure.......
there is another line below the line with "chamber":dunno:

I want to get the colors right as well.......anyone happen to know of a photo showing one of these lock-boxes?

I use it to secure my small pistol collection:D
I chain it down using the handles and another lock................
it's not a safe, but it's safe enough
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