Does anyone know the year that pre '64 70s lost the "checkering" on the rear receiver ring? I have a 375 from the late 50s that has a smooth rear ring but Ive seen some pre war models that have the same "checkering" on the top of the rear receiver as on the front. Thanks.

The smooth rear bridge was adopted about 1947-48. The serial number when the change took place is given as a range, 60000-121000, depending on if it were a standard or magnum action. Also Winchester tended to skip back and forth on small changes until all the old stock was used up. You may find one with a certain sn that has a smooth bridge and another later sn with a matted bridge.

I really haven't seen enough pre '64s to even form an educated guess. Thanks again.