Info on a 41 dated byf?

[barr44]

I have just acquired a 41 dated byf marked toggle luger. It is all matching except for the take-down lever and the side-plate, which are both unmarked. It has black plastic grips which are like the ones shown in a photo on this forum. They seem to have some raised circles with what looks like a punch mark in the center, although they are at more of an angle rather than straight across the grip as shown in the photo. The barrel has evidently been replaced but then numbered to the gun. The barrel is proofed E/655 and has the E/S proof as well. The receiver of the gun is marked E/135, which I assume would be correct to the piece. At sometime the receiver looks to have been polished and re-blued as the proofs are somewhat polished away. I don't see any sign of the the rest of the numbers or proofs being disturbed. I have been told that repairs and or re-bluing was done just after the war for use by troops from other countries or for police use. The gun has a mis-matched aluminum based mag. which is proofed E/63 or 83 with a +. What is the significance of the +. I had to fit the side-plate to the gun in order to make it function. I was also wondering if this gun could have been re-worked around the end of the war or much later. The gun looks to have worn evenly overall and the bluing on the receiver doesn't look any newer than the rest of the gun. There are no importer marks, but there is an 8,83 stamped on the bottom of the barrel between the serial no. and the receiver end. I've been told this has to do with the internal diameter of the barrel. I am somewhat new to the luger world and would appreciate any and all info, thanks, barr44. I have included an image of the right side.