What is it?

[Tolesa]

Any ideas?

[Sealander]

Tolesa,
this looks like the receiving part of a push-pin button (or whatever its name may be) Could be the closure of i.e a tent.
regards
Sealander

[RSwank]

Looks like part of a canteen cover. Look at how the flaps snap closed by pushing a short pin through the center hole of the "snap". The same type of closure could by used on holsters that had a cover flap and probably other military issue items.

http://www.ima-usa.com/u-s-ww2-cante...ard-issue.html

[David Ransome]

Agreed, It is a part of a press stud type of snap fastener sometimes found on heavier duty fabric or leather items where a button or zip might not be suitable. I suspect that it's size is approx. 20mm.

[harrison987]

Also used on parachute Bags

[Tolesa]

Many thanks, gentlemen. Size is cca 20mm, yes. Tolesa