For the small community link of collectors that obsess over these early RO QPs, there are two main variants of the dial, Mark 1 and Mark 2. The difference is easy to spot, with the earlier Mark 1 dials using a smaller font for "Audemars Piguet" on the dial and later Mark 2 dials using a conventionally capitalized and larger font for the nameplate. You can find an example of both below: