Its a museum piece.
IF.... the engine runs great, and the blades are in great shape, everything else can be gone through easily and for not much money. Convert the controls to under the seat conventional controls and then you have a flying gyroplane for under 4 grand.
If the blades are no good, or the engine is bad, then you have just a pile of old parts that have little value.
Even if the engine is running great, bear in mind these engines are the most UNRELIABLE engines you could possibly buy. Engine quitting at any moment will be the reality of owning and trying to fly this machine. To alot of people thats a big turn off. Knowing that you'd be a fool to try to fly it anywhere out of the pattern at the airport.
The engine has no muffler of any kind, so its going to be SUPER LOUD!!!
I personally wouldn't give more than 1500$ for it, assuming the blades and engine are good.
I agree with others, that you would be far better off building a gyrobee from plans than fooling around with this thing.
If you are not super heavy, say 150 -170 pounds, you might could fix up this bensen and replace the Mac drone engine with a Rotax and upgrade a few bits and pieces and end up with a decent gyro. But I would rather just build a gyrobee if I were wanting a cheap gyro and wanted a project to work on