Hi Joe, yes the Germans did issue magazines without numbers to Armorers, but all Military Mauser Magazines with aluminum bottoms that were issued with pistols were numbered, except in the late 1941 and 1942 byf Lugers. Then some fxo aluminum bottom magazines issued with these Lugers might have been unnumbered.
The fxo series of magazines were issued in 1941, so it isn't proper for your 1937 Luger.
Hope this helps!