Seems to me highly unlikely there are many of these hanging around in people's attics so, in that sense, it could be termed rare.
But unless you can see similar items changing hands on the likes of eBay, it's going to be hard to put a value on it. Realistically, it's one of those things that is basically worth only what somebody else is prepared to pay for it.
If you can find another Genesis fan who has always wanted one, you're potentially in luck!
Thank you for the info