aluminium ww2 magazine questions

The aluminium mag bottoms started appearing around 1924-1928 or so. There were several different types of mag bodies, makers, markings and bottoms. They were not all marked. In addition, since aluminium is easy to "work" many originals have been buffed, re-numbered and re-proofed, and by this I mean postwar. Several other countries, including East-Germany have made mags for their military and police as well as re-marked WWII mags, so it can get confusing. IMO the best way to know original WWII era mags is to handle the originals and second is to examine the major references.