I was told that mine was a 1980, but per my documentation, it is a 1979 Gola 459 model from April 1979. Model #3-290. The model # is more a designation in the event that the man that originally ordered your Gola did or did not add any custom options. You won't find any info on the internet about the model number, that is a Hohner internal number and not released to the public.
Talking about Golas, I found a video that is a COMPLETE surprise for me in that I found a video that has *2* PA Gola 414's and they are playing along to a... wait for it... Roland BK-7m.
I have a BK, and of course an 8X and the Gola... I may be uber-strange saying it, but I feel it's almost heresy mixing the Gola and digital worlds, and that is even after me seeing a Gola with a MIDI system installed... lol
Anyway, enjoy the video.