The New Model solved the issue of accidental discharge from an inadvertent blow to to the hammer, which was possible with the original 'old model' action. In order to fire, the transfer bar must be in a raised position, and the trigger must be pulled for the transfer bar to be in that upper position. The transfer bar acts as an intermediary device that transfers the impact from the hammer to the firing pin, rather than having the hammer come in direct contact with the firing pin. It took a few more years for Ruger engineers to solve the transfer bar problem with the Bearcat, so the New Bearcat did not emerge until 1993. Ruger introduced the New Model line of Single Six, Blackhawk, and Super Blackhawk revolvers that incorporated the transfer bar safety mechanism in 1973. So I think a guide for detecting the conversion kit in online revolver pictures may be helpful. And when those are auction guns that get bid up to collector grade price, I can only imagine that the buyers are disappointed when they receive those guns, only to find the transfer bar safety installed and no original parts present.
Sometimes I see guns advertised that I can tell are converted, but the ad doesn't mention that fact.
