Factory Order numbers with a letter from 1952 to 1961.
Factory Order Numbers (FON) with a letter from 1935 to 1941.
FON consists a batch number of usually four digits, followed by a one letter (sometimes prefixed by a space) followed by one or two digits (ranking).
The numbers appear as the 5th and 6th digits in the serial number.
This information has not been officially confirmed by Epiphone.
Where to find the serial number The serial number is stamped or punched on the back of the headstock or acoustic in the sound hole.
The acoustic models are manufactured since late 1989 in Bozeman, Montana.(After 5 9999 came 510 000) Evidently the production was high in 1956 because "6 9999" is exceeded.Also in 19 there was a high production, "9 9999" is exceeded for "932 000" or higher.When a six-digit serial number is concerned, there is no space, because the highest number in four digits (9999) has been exceeded and so fills the space. In 1955, Gibson forgot to put back the serial number range to 0001. For this reason, the array of four-digit serial number was exceeded after 9999.Thence 5 digits and no space between the year (5) and the serial number.If follows there is a third letter E, it stands for Electric.