Sorry to disagree with you gatorcpa, but as per my recent post, this model is often (incorrectly) called a Respirator and there is quite a bit action on them.
First of all, it's an 18K case and strap. By the way, that eBay listing (cro23) is from a fantasist, the price is way too high and the dial is appalling. Disgusting, badly refinished by an unskilled and blind amateur. I'd be surprised if he gets $800 for it, myself.
So cro23, you could could do pretty well on it, but on eBay, you'd have to sell it as is, I reckon, as the mechanical condition and dial mean that someone will have to do some work on it. And you don't sound as though you're in the watch business to being with. In an ideal world, it should equal the value of the gold as scrap, but you'd have to know how to sell it properly and where, and that's a bit more complicated.
Sorry your grandpa was a tool, and best of luck with it.