Looks slightly too small to be a 37mm.... 20mm perhaps? The uniforms and terrain would indicate Africa, so my guess is 5th Light Division, Deutches Afrika Korps. Probably to early to be in Panzer Armee Afrika.
The guy on the left appears to be using a 70cm Entfernungsmesser 14, or 70cm Range Finder Mark 14.

Also the troops are using M40 Tropical tunis, and M35 Stallheims. Can't name the gun, so I'll name everything else.