Here's my steel rim M1. It looks like WW2 according to the chinstrap and front-seam.
But on the site toppots they say when they changed from stainless steel to steel rim
the seam went to the rear. But maybe as there are stainless steel back seam rims, there are
steel rim front-seams also. If you look closer there are remains of white bars on the front, the left one is really rectangular, maybe captain bars??