Hi Vilo,
they were amazing in thier day, came out about 20 years ago. I think it also predates GM standard. Here in Aust, even the floppy disk drive was an optional extra.
My memory is a bit fuzzy on it, I sold mine about 17 years ago.
Don't know if you'd be able to get something that old fixed if not working correctly. Technics stopped producing keyboards in 2004.

Price wise, wouldn't have a clue if it's worth it or not.

best wishes
Rikki