Lifter Ser # 18070
 

Lifter serial # 18070 arrived on my door step last Saturday in the hand of the gentleman that called the evening before. It is a 2 frame made in 1880. Quite nice condition overall with one replaced screw on the trigger guard and frosted bores.
The BOOK provides that it is a PT-U-0-P-10-30. All match (gun and book) except the 10 gauge part. The bore will not accept a 10 ga. shell. A 12 Ga. is loose. I tried a Parker 12 ga. (A) brass case and it fit perfect. Would this have been chambered for this brass case at this date?

Yes. Check the chamber depth and also check to see if the chamber ends abruptly or if it transitions to a forcing cone.