1966 fg180

The value varies greatly on the condition, playability, and the audience.  I'd say $300 to $1000.

I have a 1967 FG-180 that I paid over $400 for, specifically as a rescue.  yamahavintagefg.boards.net/thread/410/1967-yamaha-green-label-reset  It's possibly worth twice what I paid, but I'd never get back the value of all the work I put into it.

That is the problem with most vintage FG's.  The cost of the work to properly make them playable is typically more than the guitar is worth.

Can you share the serial number, and possibly the internal date code, for my list?