Sourdough, thanks for the help. Here are a couple more pics as best I could do. I'm trying to show that, at half cock the bolt is well below the frame and cannot contact the cylinder. One pic is with the cylinder removed and one attempting to show the gap with the cylinder in place. That it why I thought the damage to the cylinder has been done by someone holding the hammer part-way back but not quite to the half cock position. That's the only way I see to make the bolt "rub" on the cylinder. You might be right if there is something that I don't understand or I am not seeing. Also, the scratch is not "consistent" all around the cylinder, but deeper in places, like thumb pressure on the hammer varied while the damage was being done?
View attachment 24523 View attachment 24524
In the second pic the gap between the frame and the bottom of the cylinder can be seen just above the reflection. The bolt, if it were up, proud of the frame would be about where the reflection is. Both these pics were taken with the pistol at half cock. Thanks again, and tell me what you think, please.