Presented in these photos are two textbook original M42 field caps, worn by German Army soldiers in WWII. The one on the left (or on top) is from 1942 and is a size 55. The one on the right (or bottom) is from 1943 and is a size 56. The caps differ in the following ways:
Air vent size and finish
Bobbin thread stitching style
Insignia shade, positioning, and relative size of graphic elements
Relative size of scallop on front flap, also height of flap and shape of flap end
Button material and color of stitching
They made these things by the millions, many manufacturers made them. They weren’t able to make them all the same.