Chris,
Cool luger! The matte/shiney finish on the receiver near the date I have seen before on early salt blued 1937s. Looks like Mauser was using up the remaining rust blue parts as they were changing to all blue guns. Check out the post by "blcman" (post #205) on Jan Stills forum in the 1937 data base.
He has #1164t and states the "frame has a odd dull finish". Maybe his is similar to yours.
http://luger.gunboards.com/showthrea...t=3206&page=21
Tom