is the diamond jubilee medal real silver (?)
Err, no, don't be daft. Not in the slightest. It is made of "nickel silver" which contains absolutely no silver at all, being an alloy of copper, nickel and, usually, zinc (somewhere on the order of 3 to 1 to 1).
The Silver Jubilee medal was, indeed, silver, as was the Coronation medal. There has always been a strong suspicion that the Golden Jubilee medal is made of compo chocolate with a gilt wrapper.