My 1877 Lifter 12 gauge has textbook standard chambers for our modern shells. Back then, the 12A would have been one of the proper choices. In 1881, WRA Co. sold both paper and brass loaded shells. The catalog has no reference to 12A, which may have been a UMC and/or Parker shell designation, I dunno. By 1886, the 'A' designation may have been obsolete. The 'B' designation was old news by then. Cheers!

Thank you for the information.

TC