The type "A" are struck from business struck dies. Type "B" are struck on reverse retired proof dies. The difference is in a few devices on the reverse. Here is an example of each. They are found on 1956-1964 Philly quarters.
type A

type B

The type "B" are business strike coins with the retired proof reverses.
type A

type B

The type "B" are business strike coins with the retired proof reverses.





















