I believed that, in addition to the trigger guard, the cylinder had received a good scrubbing as well. So heat did that? I do shoot this gun, but not frequently enough, nor rapidly enough, to cause this, so, again, caused by a previous owner.

The trigger letters as such. Later, I will locate the factory letter and provide the exact wording. Any reference to knurling is mine, and Roy's letter might reference it as knurling, or checkering, or...?