Your pump is probably not the original pump. T&N will probably be able to tell you for sure. Mine is an aftermarket unit rather than an AC original. The aftermarket pumps made 30+ years ago are as good as the originals when properly restored, unlike the modern versions.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)