I've been researching the history of the Fender F-series for about 5 years now, for the simple reason that there is a serious lack of information about these guitars on the web. My website is www.philsfenders.com and all the information on the F-55-12 can be found there. I have been unable to trace any serial numbers that identify the year of manufacture. No accurate records were kept. On some of my guitars the date is actually stamped on the neck block and sometimes on the rectangular label inside the guitars. It worth having a good look inside. You can also roughly date the guitar by specification as well, as subtle changes were made throughout the 70's.