Can't tell you about the very 1st 40X, but I own #0030 and another one just a hair higher number and saw another lower than these 2; all of them were stamped with the model number. I've owned over 100 and looked at many others and never saw a 40X that wasn't stamped with the model (except a rimfire model that obviously got out the back door before it was finished or even had a serial number). I still wonder if the model # was sanded/buffed off the OP's rifle, since it is a shallower stamp than the Remington stamping above it.They are several 40x out there like that was not stamped all 722 were stamped the first 40x was not stamped they came with heavy barrels and stocks.