Gold medallion, no number - I'd say most likely early post-WWI, but pre-1920. The progression was from inset gold medallion, to no medallions in the 1920's, then flush silver medallions from around the early 30's until WWII. There was a brief interlude in the early 1920's when the target stocks were supplanted by ones that were like those found on the Regulation Police.
You might want to take a look at the following thread to see all of these:
.22/.32 Hand Ejector (Heavy Frame Target, "Bekeart" type) Pictures