Is this finders keepers?
The last sentence would indicate he owns the find. But I don’t know.
I laugh whenever someone says that. When my boy was four he found something on the ground and said, "Finders keepers, losers sweepers."
Surely, you jest. The state will take their cut and leave the finder with what they deem is "fair".
Here in America, many states have antiquities laws foisted upon us by archaeologists' influencd lawmakers who have placed a cut-off time limit for finds, after that length of time, the find becomes property of the state without any "finders' fee".
My state, NC, has set that limit at 100 years. If an item is or believed to be 101 years old or more, it is the state's.