Is the serial on the case back or on the movement? For dating the watch I assume I use the serial that is on the movement which is #15012727 The Case back has #11473603 is this an omega serial number or the case manufacture serial number? Also note the PF stamp above the Omega balloon logo. Any on know what PF stand for? Is it unusual to not have 18K or .75 Gold marked on the case back? The on thing I see is the an eagle hallmark on the case lug.
IIRC, that same case maker has been discussed on here before, and he was identified. Try doing a search on these forums, the info should be here.
The serial number on the case is the case maker's serial number and in theory, that should date the case. The movement serial number is the Omega serial and that should date the movement. As with the English made gold cases (Dennison and others) the movements were shipped bare and cased in the recipient country by approved casemakers (hence the old Omega logo inside the caseback). Sometimes the 'age' of the case is slightly different from the 'age' of the movement - all this means is that one or both went into storage prior to being cased. Usually on French cases the 'eagle's head' stamp is all you get to denote 18kt. I've searched and searched for the casemaker who used that PF stamp but had no success.
A recent thread here regarding the Fab Suisse Omegas. http://omegaforums.net/threads/fab-suisse-roll-call.20625/ You can see a lot of the same case markings in the pictures although no manufacturers name is mentioned.