Quoted from fns9l:LTG,
I just spent an hour going over the case inside and out, the headboard, and underneath, as well as along the edges of the playfield. I did not find a date or a date tag on any of it. I was quite thorough in my search. This conclusion leads me to believe that potentially this machine was not assigned a build date, possibly due to the fact it was the first prototype, and not a production model. If you have any information on where the build date should be located, I will gladly investigate it for you.
Have you removed and looked under metal apron, then you see more of top of playfield.
Worth a try.
The price: OP, we all want what we think something's worth....and there's the what its actually worth. In a way many posts so far are trying to explain this to you.
There is also a lot of seasoned individuals here, with a lot of experience in coin op industry.
There is just no such thing as a 65k prototype.
Even if it's #1.
Fair price.....15-20k.