willysmjeeps.com

If the serviceman bought it surplus in Europe and used it there before shipping it home then that is why the number was stamped onto the frame rail. It was also a common occurence in military field depots that rebuilt many jeeps at the same time to stamp the jeep's serial or registration number on the key components IE chassis and tub and etc.

Here in Darkest Arkansas we once had annual inspections,
but dropped it because it wasn't doing any good in return for
the hassle. Service stations loathed it. If you do get a blank
fender plate, check out how others were stamped, so as not
to get too physical when you stamp your numbers. It's AL
and easy to stamp. Service inspection stations probably do
not have much experience with HMV.

Jim