James Tufts Napkin Rings - how to value

How to value James Tufts Napkin Rings. How do you distinguish rarity? I own this one. Someone wants to purchase it and I want to be fair all.

An identical napkin ring sold via an online auction site (not Ebay) in 2018 for $160. More conventional Tufts napkin rings with figural additions have sold for as little as $15.

Thank you for the info, that helps a bit. Much appreciated!