I used one back in the 80's. It worked fine; but was nothing special, as has been mentioned replacement mags can be hard to find, even when the gun was new, the owner had to mail-order them from the US.
Seriously, when decent quality, brand new handguns are available in the $350 price range, how much can an orphan like this be worth?
I'm thinking Deckard is a little low, I'd offer $150, plus $10 per good, functioning mag, and I'd want to test them first. And I'd pass on the whole rig if there were less than 5 mags.