How many versions of Caliber 1300 are there?

Hi, I am a regular visitor of GO forum but almost a stranger here. Last week, I decided to try something new so I snaped a Pt FP Journe Octa Reserve de Marche with PG dial from an internet dealer. I am not sure if I will keep looking for other Journe timepieces but at least I am very happy to what I have got.

Over the pass few days, I spent sometime to gether relevant information about this watch and surprisingly found out that caliber 1300 that Octa Reserve equips with has at least three versions: (1)brass bridge with straight cotes de Geneve, (2)brass bridge with circle cotes de Geneve and (3)18K gold bridge with circle cotes de Geneve. Given the short history of this brand name, I am a bit confused on why Mr. Journe has to modify this caliber so frequently. My other questions are: is there any other version out there? and what are the major differences among these versions in terms of functioning and finishing?

Comments and advices are highly appreciated.

Best

zmxu