Bringing this back up... for additional clarification. I am not sure I get any consistency from what I just read.
I'll add mine to the mix
I did buy this one new in the box in April of 2009.
Serial number starts with 92XXXXXX Right side of Barrel roll mark shows New Haven Connecticut but oval with JM on LEFT side (same side as the roll mark). This appears to be a true Marlin made in CT gun. However add that a 336 with a serial range starting with 92 was built, delivered and sold in early 09.
To add to that, an Xs7 I just bought that was used. Shows a Kentucky made roll mark and serial number starts with MM. An oval with REP inside it on the RIGHT side of the barrel (opposite side from the roll mark) with a 6 in front of that oval (outside the oval). I don't know the age of this one but it obviously must be a Remington overseen unit?