model 6085 question

[adeldellosa]

hello newbie here,

i got a rolex model 6085 (18k YG) with serial# 7939** which falls in the production year 1951 based on google (BECKERTIME)

in my curiosity, i opened it and not sure if it has the right movemement/mechanism (caliber 645) there are two sets of numbers inside, it has F18010 and on the inner part has 15850

my question is, does it have to match the casing's serial number 7939**?

i cant post photo yet, hopefully soon i can :)

thanks!