'Used' guitars are often dumped off by Epiphone at auctions where less than scrupulous dealers buy them up, slap whatever parts they have to complete them and then sell them on E Bay with some concocted story and should probably be avoided though there are those who claim to have bought them with no problems.
The headstock also as Morris stamped where you would normally find a serial number on a guitar. The seconds are usually cosmetic or minor, easily repaired things where the 'used' guitars usually involve something structural. These guitars came with a stinger from the factory at the time. Guitars marked 'used' are guitars rejected by Epiphone for something serious enough that Epiphone doesn't want to stand behind a warranty for them.things like bad neck sets, misaligned bridges, neck twists, etc. Hey there -Ive been told of an SG special, serial number 92491356 for sale - its been bashed about a bit though - literally. Either way they're warranted and can be very good values. With '2s' seconds it's usually a very minor cosmetic flaw or maybe a discrepancy in the color, often undetectable and 'B' stocks items are shop-worn or customer returns that didn't come back as pristine as they left. They usually have minor finish flaws, some undetectable. Also, a guitar I bought there had a FAKE serial number that they put on there.
It's a true factory 2nd, often sold as 'B stock' at GC, etc.