Magazine: Original or Repro?

Just took out one of my Lugers for a fondling session, as this one hasn't been caressed for about three years. It is a 1920 commercial, 99%+ with outstanding straw, a condition often encountered in this model. However, for the first time I noticed that the unmarked wood bottom magazine is blued, not bright metal. The bluing is not of the almost black variety found in WWII mags, but a very light blue similar to the rust blue on the pistol itself. In all other respects the mag appears original, but I can find no reference to blued magazines during the Weimar period. Your valued opinions, please.