The bastards will steal it from you and you’ll get nothing but a “certificate of appreciation.” Leave the country with the coin, find a Jewish collector you can trust, and sell it at market value privately. Or just keep it in your family if you don’t want the money. Don’t let them take your property for nothing.
From Times of Israel. An 8 year old girl found a machatzis hashekel minted on Har Habayit during Bayit Sheni:
On Wednesday, the coin was handed over to the archaeological unit of the Civil Administration, or COGAT, which overseas Israeli government activities in the West Bank. According to Israeli law, all archaeological finds must be turned over to the government. Hallel received a certificate of appreciation for her find.
Hallel said she was a little sad at first to turn over the coin, but got over it. And as for the feeling of holding something so historic in her hand, she said, “I felt that wow! It was written on it ‘Jerusalem the Holy City.’ That’s really exciting.”
The Jewish Libertarian 
There are some members of the Isreali government that enjoy confiscating lands,too. For example, the lands near the city of Alad,which were purchased by Jewish individuals at the time of the Ottoman Turkish control and handed down to their heirs were confiscated by some worthless beaurocrats in the Israeli government.This is nothing but shameful landhogging theft,those responsible should be thrown into jail.
http://www.timesofisrael.com/too-good-to-be-true-8-year-olds-rare-coin-not-an-ancient-artifact/