WILLYS Embossed on Rear of MB in What Year?

In what year(s) did W-O emboss WILLYS on the rear of the model MB?
I thought I had a '45 ... frame stamped 321968. Titled as a '45. A guy at a car show said W-O only stamped WILLYS on rear in '42. Is that right? I remember reading that the War Department made them stop stamping the Jeeps but do not remember when ... assumed it was the hood stamp. I may have a hybrid??
Thanks,
Phil

I could be entirely wrong but i believe the 41-42 had the script. Then was removed until 45. I think?

I believe 56willys is correct in the '41-'42 range. The government didn't want to advertise equipment manufactures on the equipment being used for the war effort... Although Ford never did remove their embossed Ford from the GPWs.