Hi all, I m new to this Forum. I have a question regarding the 324 caliber. I have noticed there is an engraved number after the number 324 on the caliber. 324 / 393. Does anyone know what it refers to? My friend's 5167A ( tropical starp) only has the 324 engraved without the 393. Does anyone know why the inconsistency from Patek? The watch was bought on 2012 last year. Any insight will be appreciated greatly. Thanks!!