vintage folding penknife in gold filled case

This little guy is barely 2-1/2" long and 1/2" wide. (folded up, of course) One end is a penknife blade, the other a double sided nail file. The knife has "VOOS STAINLESS" on its end. Patterns of horizontal lines decorate its surfaces, there's a blank box on one side in the middle where it could have been engraved, but isn't. Its swivel hook loop is stamped "1/20 12K G.F." plus some kind of tiny maker's mark in a circle, looks kinda like an upside down triangle with a bar over its top. (??) If I had to guess it'd be 1950's-ish but I don't really know, it could also be older than that but not so likely very much newer??