Double Date Question

I have found many cases of arsenal or factory (don't know at which level) re-pair and re-finishing on Double Date Lugers. I don't know if this was done exactly concurently with the 1920 stamping or not...As far as the question on the police Lugers, I am very confident in saying that many if not most of the Imperial and Weimar era police Lugers were Re-Blued and upgraded either at the time of the Sear and (sometimes) mag saftey addition or afterward. I would be interested in KNOWING at what level this re-work was conducted. A few months ago I got a 1917 DWM Police (Sear saftey) Luger from my Uncle, Vet bring back with two matching mags (one wood and one Aluminium bottom!) with Weimar brown Police Holster (unit marked to gun). This pistol has been period Rust re-blued. It is about 97% and has the inside surfaces polished bright, but there are tell-tale signs of pitts underneath the blue(very few, very light and minor). This finish is un-questionably period and Official, but is not the 1918 'factory" finish.

ps I have a 1962 era West-German Walther PP that I bought in Germany in about 1981. It is West German Police surplus and has been factory refinished during it's life as a German police pistol. The re-blue is as good or better as any first time Walther blue...and the slide was numbered to stay with and match the frame..this pistol was carried by the German Police after the factory re-blue....Old habits die hard!