Your rifle is not the first I have found with an earlier serial. In my data I have three other serials in this same model variation; 187xxx, 230xxx, and 235xxx. The earliest serial in the variation, so far, has been 340xxx.
Appears that Savage decided to do some cleanup of old receivers that were laying around. This variation was produced during some hard times with very low 99 productions.
I think these receivers were serial numbered and still in the white when put back into the production line years later. The stamping on the receiver ring would have been added before heat treat and assembly.
