The serial numbers do not reflect this change – Fender continued to make instruments using existing serial number schemes.The new Fender (FMIC) did not acquire any physical assets of the old company, just the name “Fender” and the rights to all products and trademarks .At least not while he was at Fender Musical Instrument Corporation.
Unfortunately, there is also some overlap in serial numbers between years — again due to the fact that neckplates were re-ordered various times from various manufacturers.
So starting in mid-1976 the serial number was moved to a decal on the peghead.
Even with the new system, Fender didn’t like to throw away a perfectly good serialized decal just because the year code would be incorrect.
Serial numbers are basically chronological, but there is some overlap in some years.
Before the later 1970’s Fender never expected the guitars to be collectable or for serial numbers to be important.
So, the company just used the L Plates not wanting to let them go to waste.