Regarding the item itself:
- On the one hand, it's an antiquity;
- On the other hand, it's one of many like it.
Those are two considerations worth keeping in mind.
Consulting with a lawyer on a matter like this is always good advice, especially if you get good news. In that case, fees can be paid from the sale of the find.
If you get bad news, all you lost was time. It's possible you may still be compensated in some other form (maybe a finder's fee); in that case, something is better than nothing.
That was kind of my thinking about the fees.