For Luger parts, The 37 Waffenamt represents the Haenel company in Suhl. They are indeed listed as producing fxo coded P.08 parts from 1941-42. That Waffenamt, WaA37, was also used very extensively for K98k rifle parts by JP Sauer and Sohn, also in Suhl; I have many examples in my collection. All I can tell you is that the 37 stamps on your magazines look exactly like the examples I have.
There is a complete listing of German WW2 amt’s codes at Claus’ site in Acrobat format for anyone who is ever interested:
Claus Espeholt