I don't have any SNs very close to C127xxx on my list, but from those I do have, I'd also say it was a 1950 shipment. I show no SNs that low as being shipped in 1951, even very early 1951. BTW, both round top and Magna grips are "Service Grips" just different styles. As opposed to target grips, combat grips, etc. Just another way of saying that a service grip pair is the normal standard equipment supplied by S&W for the majority of its guns. Before (and during) WWII, they were mainly round tops, with the big changeover to Magnas occurring after WWII (with a few Magnas being supplied before the war). Likewise there were a few round tops supplied after the war.