The owner was selling it as a "parts gun" because it had some timing issues that he said Ruger could not fix.
He had a letter from Ruger stating that the gun could not be repaired and an offer to replace the gun with a 4" blued GP-100. The owner declined (I assume because he did not have the money for a new gun) so Ruger returned the gun to him with a new box and instruction manual (SOP at Ruger).
Here is the gun:
In this picture, the pawl is the part circled in red, The cylinder stop in green and the spur gear in yellow .
I compared the pawl with one from my parts bin as well as the one installed in my Security Six. They were all identical and the one on the subject gun showed no signs of wear. I then turned my attention to the gear on the back of the cylinder.
When these get warn down too much, the pawl cannot complete the cycle: turning the cylinder all the way to the stop. That is what happened with this gun.
I found a used cylinder/crane assembly on ebay for cheap.
The gear was in very good condition, as was the finish. I installed the replacement, and the timing was perfect.
Some "experts" will tell you that these parts need to be "hand fitted". This is not always the case.
This may be the case if both parts had shown some wear, but both parts (the new cylinder and the old pawl) were in very good condition.
Also these guns are built on an assembly line in which every part is identical to the next one, so no hand fitting is done at the factory (we have Eli Whitney to thank for that!). If our guns were had fitted, we would have to pay double or triple the price. This is the reason Colt no longer makes the Python. Hand fitted guns are way too costly to manufacture.
This is another example of how you can get guns for cheap, buy the ones that others have given up on and fix them yourself.
Shooting with Hobie