I may be wrong, but it appears from the S/N of your gun that a correction of the records is in order. This gun has all the features of a Hunter gun, as opposed to the Marlin-produced ones. First, there is no "S" prefix before the serial number. Also, the forend is shaped like Hunter era guns, as opposed to the bulkier Marlin forends.
As to the stock, my guess is that the stock was cut, but cut to the correct length to accommodate the pad and leave the correct LOP over the pad. Metal originality?--- there's a "weep hole" at the forend lug, which would suggest a reblue, but I've seen a few original barrels with it also.
Do the barrels have an inscription on top of both barrels?