Hopefully there are at least 3 and I get some of my wife's Irish luck!
You never know. My statement above should be reworded to say these two are the only ones
known.
Here they are mentioned in the RENE Ref:
But whether there were a few others made is anybody's guess. There was clearly some unusual circumstance that caused these two to be made that high up into the 151 prefix since the supply of lowback frames was generally exhausted in the 151-0xxxx range (and there were plenty of highbacks in that range as well). Someone probably found a couple lowback stainless frames that had been overlooked and just slipped them into the production line. Might have just happened that they were making a batch of GA-36 revolvers when those two frames came along in the queue. A guy screwing barrels into frames all day might not have even noticed the difference. Someone fitting the cylinders and actions would have had a better chance of seeing the difference, and certainly whoever had to put grips on the completed guns would have figured it out when the highback grips wouldn't fit.