most manufactures did not put serial numbers on their low end guns, I guess it saved a few cents (no one had to change the number stamp after each gun. While Winchester put S.N. on the model 70 and 71s producted prior to 1968, you will not find serial number on any Winchester model 43.
Bob you could be right. The win 69 that is in my gun room doesn't. But IIRC when transfering a win 43 in 22 hornet, it was also missing a serial number which drove the FFL crazy. maybe an early manufacture/// I coould also be wrong, my memory got bad when my hair fell out...those could have been attached to each other LOL