Marked sterling, but where to find maker's mark, if any?

[Adam.NYC]

This little snuff box only is marked 'sterling' that I can see. Where on the box would be the most likely spot I might find more marks or is it common to find old boxes with no marks?

Based on the monogram, I assume it is American, but what period? It's 1.5 inches across.

Thanks for your help!

Adam