In good condition, there's always some market for a device like this - but I can't really advise you on price, I don't have a feel for what the collectors market demands - I will say the prices you typically would see on eBay and at non-tech shows are probably out of range of what the device is worth. I typically laugh at those prices. I can give you two things here - the Rider's manual was designed in an era when the device was in use, so you're going to see problems that that manual didn't cover, things that normally wouldn't happen in the device's useful life of 10-20 years. Other things are happening now, parts are corroding, mechanical devices are disintegrating - take the manual with a lot of "the tech using this paper wouldn't have seen this device in it's current condition." Second, don't plug it in or mess with parts internally if you're unsure. Chances are there are some shorted or leaking (electrical) parts at this point, and you could cause the first tube in the circuit to red-plate (too much current) or worse, burn out that transformer that you'll never find. If you plan on selling it, it's best to sell it "untested, unmolested, will not plug in unless you're paying." That may make some people mad, but I've seen some stuff that probably wasn't helped by plugging in with an unknown state at hand. That one's a lot more complex than most radios of the time, and it's going to require someone with know-how to physically touch it to try and fix it.