Quote Originally Posted by browningautorifleicon View Post
Looks like European...
Yep, Yugoslavian.

Sorry I'd forgotten about this one and I did eventually find an answer. Apparently it's for the Yugoicon M72 RPK, for carrying ammunition in boxes, not mags.

It supposedly holds 540 rnds in 36 boxes of 15 rnds. I haven't actually checked that these numbers are correct.