I posted here a few years ago - I have the F-55-12 bought second-hand in Avignon in 1980 with the proceeds of 3 weeks picking grapes. The number on the neck block is K109025, the same number as a couple of other guitars mentioned in this thread, and the number on the center brace on the back is T 35 7 3. Since someone in this thread bought an F-55-12 with that same neck block number in Paris in 1973, I expect that mine is also from around that year.

Looking at the posts in this thread, I'm wondering if a K in front of the neck block number may refer to Korea (probably Samick who have made guitars for lots of US companies), a Y to Yamaha in Japan, and an F to Fender in the USA. The 025 at the end of the neck block number also seems to have some significance.

My guitar does not have the adjustable bridge that I see in photos of F-55-12s. I presume that the bridge on mine was replaced with a non-adjustable one in the 1970s when a piezo pickup was fitted. I had a K&K Pure Mini pickup installed recently and it sounds very sweet even though it still doesn't put out deep bass.

I've had mine for nearly 40 years, it sounds and plays great, and it's in very good condition despite the fact that I hauled it around and played gigs with it in the early 1990s. I now have a beautiful Guild 12-string that sounds better, but that Fender is like a member of my family and it goes when I do.