Acceptance mark on barrel?

[barr44]

I have a 1940 code 42 Luger that has the E/655 mark stamped on the left side of the barrel, just about opposite of the E/S proof on the right side of the barrel. The receiver has the two acceptance marks E/655 and the E/S on the right side in the normal location.
I'm curious as to why this gun has the acceptance mark on the left side of the barrel, as I haven't seen this on other Lugers. I had read of guns being re-proofed after being repaired, but not sure about the added acceptance mark.
This gun is a marriage between a frame assembly with one serial number and the barrel receiver assembly being of a different serial number. Could this be an indication that the gun has been re-assembled as a mismatch between the frame assembly and the barrel/receiver assembly and then remarked with the additional acceptance mark? Each of the two assemblies has all matching numbers and the gun looks to have been in this configuration for a very long time.
As always, I would appreciate any information forth coming from you folks. I know the mismatch is very questionable, but am wondering why the second acceptance mark.



Thanks, barr