Dwight, an interesting question that I do not know the answer to. It would appear in the Weimar era the magazines were replaced or repaired piecemeal based on the information in Gortz and Bryans "German Small Arms Markings." On pages 132 and 133 there is a copy of an order concerning new magazine bodies and referencing a spare parts list including 6000 magazine bodies, 8,000 magazine buttons, 6000 magazine bottom pins, 6000 magazine spring holders, 3000 magazine followers, 6000 magazine follower buttons, 10,000 magazine springs. . .
This order is for the extruded body magazines and is not capable of producing 6000 magazines being 3000 mag followers short. It is also long 2000 magazine buttons and 4000 magazine springs.
My Weimar police reissue 1915 has a Haenel-Schmeisser magazine with a wood bottom that is numbered to the pistol, perhaps the original was salvaged or another wooden bottom was renumbered.
However the Imperial usage may have been different with gross numbers of intact magazines being ordered as replacements. Since the imperial magazine bodies are not numbered to the gun, replacement of a bottom with a different numbered bottom would not be apparent.
Some information on armorers practice or field practice 1914 to 1918 would be interesting.