Wow, that's a really cool fan! I've definitely never seen one like that. Not sure what it's worth exactly, but I bet you could get a bidding war started on eBay if you listed it at a low-to-moderate starting bid. But I think it's a good idea that you keep it, as these things must be super uncommon. It's definitely from the 70s or so. Welcome to DT by the way!
I've had this fan for about five years now, and it's just sitting not getting much use. What does an F-1280 go for these days? I know they're quite rare in good condition.