52c sporter with no proof mark|Winchester .22 Rim Fire|Forum|Winchester Collector

I came across a 1958 52c sporter 97xxx serial range.  I am not familiar with c’s made this late.  It has a plastic butt plate which I have only seen once before and the front sight ramp seems to be a bit different. It seems to sit to close to the muzzle and the groves for the sight hood look more cut into the ramp instead of milled?  But the real head scratcher is lack of proof marks on receiver and barrel.  The gun looks correct in all aspects as far as stock configuration and barrel markings.  70’s are more my specialty and I have seen a similar ramps on 62-63 70’s  and I believe this ramp is brazed on and not forged as part of the barrel.  I think that is how the last sporter barrels were made.  But the proof marks has me thrown. Any help or suggestions would be appreciated.