YUGOSLAVIAN M56 LEATHER POUCH 

 Manufactured in the 1950s-60s, has an all leather construction, 
Was designed to carry four mags for the M56 SMG,

Has a fitted adjustable leather shoulder strap and have small pocket on the strap
 which is most likely for an oil bottle or cleaning kit.

 These pouches were also were great for MP40 and Thompson mags,
  if you have seen the movie Kelly's heroes you can clearly see these pouches being used by the cast.