Not trying to horn into your business deal here but HUH?
He {Somehiker} said
the finders fee comes from the buyer to the guy who found the seller (you) so it is not one cent out of your pocket. Did you misunderstand that? I see this all the time at auctions where they charge a 'buyers premium' of ten percent, which
does not come out of the sellers pockets.
If that is a genuine gold nugget and not a lump of copper or lead plated or painted brassy yellow, it is a nice nugget. It does look rather like a "home made" "nugget" melting metal and pouring it into water or sand to make a fake "nugget". I hope that is not the case.
Congratulations on your upcoming retirement - hope you have a great one.