Barrel replacement?

[barr44]

I have recently acquired a 'byf' 41 marked luger, sn. 42xxa. All of the numbers match except for the magazine, the side plate and trigger which I had to fit to the gun, the side plate is not marked at all, so I suspect that it is a an after market piece. The take-down latch seems to have had the number filed off. My question is about the barrel which has the sn. of the gun stamped on the bottom and also 8,82. The barrel of the gun has the E/S and a E/655 proofs whereas the receiver has the E/S and E/135 proofs. This indicates to me that the barrel was replaced. The barrel bluing looks to be original as does the bluing on the frame, while the bluing on the receiver looks to have been redone as the proof marks are definitely polished over as they are not as sharp as the rest of the markings on the gun. Overall, even with the refinish work on the receiver, the finish on the piece seems to all show about the same amount of wear and age. The rifling looks to be very good with little or no pitting with strong lands and grooves, while the outside finish of the barrel seems to match the finish on the rest of the piece. I suppose there is no way to determine when this rework was done, but I'm just wondering if this type of repair would have been done during the war. I have enclosed a couple of photos and would appreciate any thoughts on the subject, thanks barr44.