Womble,
The muzzle end of the barrels show signs of shortening by a small amount or, at a minimum, the ribs coming loose and misplacing the end "plug". Nominal barrel lengths would usually be in whole or half centimeters, with actual length sometimes differing slightly due to finishing, "striking" or possibly mistake. Determining the model number might reveal a choice of available nominal barrel lengths. I wouldn't be surprised to find that the original length was 76 cm, but I wouldn't disagree if told it was 74.5. The marks at the chamber end may have resulted from "peening" to tighten the fit, however this is conjecture.
Mike