Win Laboratories Phono Preamp Value???

I have the opportunity to purchase a phono preamp made by Win Laboratories (Dr. Sao Win). It's designed for a MC cartridge, and has LOTS of gain! It is powered by a "wall-wart" looking AC transformer, but with three wires going to it, so different than the typical wall-wart. I don't know what such an item would be valued at. Anybody know? Thanks.
Just a bit more information. The unit is a simple metal box, about 6" long and 1.5" square, with a paper sticker on the bottom that states Win Laboratories and S/N 1529. No model number. The original owner was a colleague of Dr. Win's, so I'm not sure whether it got all the packaging and labeling that others do. It has nothing but RCA inputs on one end and outputs on other, as well as a ground terminal. The power cord also comes out of the metal box and is not detachable. Pretty simple looking, clearly not trying to be good looking!
Are you sure this is for an MC cartridge? It might be a PSU for the Win Strain Gauge cartridge, a preamp that will not work with MC cartridges....
Ivan - yes I'm sure, as I've used it with my low output (0.30 mv) Denon DL103r cartridge with good success. It must provide atleast 70 db of gain.
Bluebook on the Jewel preamp 1985 is $250 retail; about half that wholesale...Don't know if that corresponds to your prepre. From the description it sounds like it should be in the $100 - $150 ballpark.
It's a nice unit. Certainly desirable at that price....