Early Snap On piece that I need to know what it is!

[jimsbeercans]

I hit collecting Snap On.com and found nothing about this piece. Part number KR413 and dated 1956.
Looks like a parts bin but not sure. Missing a few key items that would of helped.

But, since we have older mechanics on CABE its worth a try. Any help will be appreciated.

 

[T.J. Higgins]

 

[jimsbeercans]

WOW. Thanks. Never even thought is was for diag. meters. Thought along the lines of tire patches or valve stems. Thanks again and where did you find it? Incase you have a different site then the one I have.