It is not true that chamber lengths were not marked until Marlin bought Hunter Arms in 1945. I have a 1933 16ga field that is marked 2 3/4" on the barrel flats, and a 1936 .410 that is also marked 3" on the flats. Both these marks are in the style of the WF/LR marks with the length in the center of arched lettering. I also have a Marlin built 16 from 1946 that does not have a chamber length stamp on the flats. Others I have seen from the Marlin era have the chamber length stamped in a straight line close to the barrel lug. As to "butchering" a gun by lengthening the chamber to a more useful length, that is your personal opinion, and not one that I share, obviously.
