How do you know thats not copper?Looks like an honest 1918 DWM Luger that needs a good cleaning inside and out. (I see rust in the bore) Go over the exterior with an oily cloth and clean the bore with a good solvent and brush. It should present itself quite well.
The holster is interesting and unusual. Lugerholsterrepair on this forum can repair the broken strap and anything else that needs attention on the holster.
You have a nice Imperial Luger that's well worth preserving.