QUEEN We Will Rock You - Sixpence Coin (Official US commemorative sixpence coin which was minted in 2004 and still housed in the original bubblepak, features the head of Brian May on one side and a BM logo on the other. This is official merchandise that was produced exclusively for the show at the Paris Theatre in Las Vegas, the store has now closed making this item unavailable anywhere else. link
He also wrote about that item in his Soapbox few years ago as I remember...
There have been three editions of the sixpence.
One produced as merchandise for the BTTL tour in 1993, one as above for the Vegas WWRY production, & another for the QPR tour 2005.
The last two are not (yet) valuable. The first one is.