I recently acquired a Taylor baby rolling block in 45 colt. Plinked with it and decided to clean the bore. After cleaning I decided to examine it with one of the Teslong endoscopes. See the attached picture. Apparently the reamer had a defect and it left the transverse mark shown. The mark appears at regular intervals, which makes me believe it was a reamer. So far I do not believe it causes a problem. These cheap scopes find things that maybe we do not need to know about.