Lee, I know of only two pair, one I owned back in 2006 but traded it to some one, maybe Lyle, at the SLC meeting. The insert though had a crack in the bottom near the grip pin. This was probably caused as you stated, trying to put it in place on the gun. The other pair was in the last Amoskeag auction fitted to its original K-38 and numbered and factory lettered to the gun having shipped in 1950 to of all places, the Salt Lake City Police Department. I almost bid on this but resisted the urge somehow.
Chuck