should have a date on it, it's a crown, who's on the front? I have got a couple of Churchill crowns and a couple to celebrate the Queen Mother's something-or-other, I must find them and see if they are in good order. I don't think they are worth a great deal since there were a lot issued of the ones I have, but it depends if yours is mint uncirculated. A coin dealer would tell you for certain.
The description sounds like a 1960 New York Exhibition Crown which is apparently the scarcest commemorative crown issued in the reign of Queen Elizabeth II and could possibly fetch a few pounds depending on its condition.
Half a crown was 2/6p. (Two and six) A crown is therefore 5/0p. (Five shillings). That means in today's money its now worth 25p. Unless it's an unusual crown, in mint condition, where it might be worth a bit more. Perhaps you should see a coin collector. Good Luck!