The s/n is sometimes ink typed on a label where it should have been letter pressed.
According to Wiedler Epiphone often applied a newer type label with the old s/n typed in when a guitar was brought in for repair.
This manifested itself in the form of a blind stamped number between three and five digits, usually located on the top rear of the headstock.
(Fisch & Fred, , page 225) Wiedler wrote us June 2013: “The Electar series started at a lower s/n than 3-digit. Until circa 1938 the s/n stamp is located on the top edge of the headstock.
he easiest way to find the year of manufacture of a particular Gibson guitar is to reference the instrument's serial number of factory order number.
The Masterbilt serialnumber system did not start with the number 1000 but with the number 5000. The serial numbers were blind stamped on the interior back under the bass f-hole, generally below but sometimes on the (oval) label, maybe even without a label like the earlier Recording and Seville models.
From about 1934 forward, the serial numbers were ink typed directly on the label (Long Island label) or letter pressed on the label (rectangular Masterbilt label, Green label and Blue label).
Another thing to look for is whether the numbers are too close. The fake one on the right has no serial number at all. You can search for your serial number at The Guitar Dater Project.
It will return the birth date of your guitar and the manufacturing plant.
By the 1930s, the company was also making flattop acoustic guitars, as well as one of the first commercially available hollow-body electric guitars, used and popularized by Charlie Christian.