Well , thank you so much for your help, guys but I still think there is something fishy with this instrument. I inspected the interior with an endoscope camera and there is no visible sticker or label inside. There is no branded sn neither inside or outside. I am deadly sure that I bought the guitar in late 1984 or early 1985, as she was there before my wife, which I met in summer 85 and she (my wife) admits reluctantly that the instrument was there before her. Here I attach another picture of the backside of the body with a sticker saying Sheraton-VSB. Some years ago I put a protective tape over it, as it started to peel off. But it is still in the same position. The flash modulated the colour, it is a golden label with black letters.
The serial on the rear of the headstock would fit only to a Nashville Gibson of the year in which I bought it as it has only numbers none of which meets a factory code of Epiphones . Punching the serial online into the input of the epiphone section of the Guitar Dater Project yields no result, whereas the output in the Gibson section is Jan 20th, 1984, 31st instrument. Very strange. I do not think the instrument itself is forged, as it is extremely well crafted and has not changed in the 35 years that I own it. The varnish looks like new, it has not worked and it is absolutely in tune. At the moment I can just imagine that someone took a Korean Epiphone of the earlyy 80 th , removed the label in the hollow body ( though there are no signs of that) and put fake stickers on the head and body to make it look like an American instrument. That would be nasty but I can live with it, as it is a really good guitar which I do not want to sell. But then this still would not fit to the 'Epiphone by Gibson' inlay . Quite a mystery, but I would still like to know where it was really build.... Perhaps it grew on a tree like this. Anyway, thank you very much again for your helpful comments , I really appreciate your engagement. Have a nice weekend