I know you have heard this a million times, but it hold's TRUE.
The value of a coin is what a person is willing to pay.
Price guides mean little, by the time they are printed the market has changed quite a bit and prices may be higher or even lower for a coin.
Now IDK what kind of variety it is. I have no idea what S-104 means. I think your talking about the LIHERTY one, right? That's a sheldon 103 variety.
I'm seeing them selling for around $750, and thats S-104.
It would be best to have this slabbed. NGC is prefered by many numismatists.
I would spend the $30 or so and have it slabbed, this might make the coin bring an extra $100 as it's a bit of security blanket to collectors.
I WOULD NOT sell it on eBay, way too many scammers. Consign it to heritage auction (
www.ha.com). They have rather low fees and they take clear photographs for it.