P37 Backpack with Straps Blue-Gray Belgium Post-WWIIVintage Belgian Air Force 1937 Pattern Large Pack. This classic British designed backpack comes from the 1937 Pattern Web Equipment set. It is a heavy duty cotton canvas material with brass hardware. The air force blue gray color varies as shown. Condition: All are genuine used military surplus and may have names or numbers written on them, frayed edges and minor holes or tears. Excellent Less use, minor or no rust corrosion on metal parts Very Good