It screams "rare", and it is a unique machine. I've never seen one in the flesh, and I'd love to, if given the opportunity. "Rare" does not translate to "Valuable" or "desirable". GTB "Raven" is also "rare"

How much is it worth ?

Depends on how much you are willing to pay. If is it your "Holy Grail" - then money is no object.

Sounds like $2000 would be a starting point, although a 9/10 for a machine this vintage would be very rare.