What would a Carson City mark on silver dollar look like?

Assuming you have a Morgan dollar with Miss Liberty's head on the front and a spread-winged eagle on the back, the mint mark position will be above the DO in DOLLAR. Carson City is identified by "CC", San Francisco by "S", New Orleans by "O" and Denver (1921 only) by "D". Philadelphia coins didn't use the P mint mark back then so they're blank.