Target stocks do run in that period and do look period to me, the correct ones with the diamond. Magna stocks from that period are numbered on the right hand grip (see photo below) but they don't have the "S". These shown below are from 1955 and would work on your pistol.
Target stocks were available as an option. During the time your revolver was made, it could be ordered with target stocks, most likely the non-relieved type, although relieved stocks were introduced around that time as well depending on when your gun was shipped.
Below is a pic of numbered magnas from 1955 which would be correct for your revolver, and a pre-27 from 1955 (5") with relieved target stocks. I suggested relieved target stocks because appearance wise I think they work better on your revolver.
By the way, if you show a picture of the inside of the grips, someone here may recognize them.