Bit of a spotter question - but what's the diameter of this medal? Is it, err, Queen-sized like the QGJM?
Spotter question deserves a proper answer! (makes a change from all those silly Wah posts anyway
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Since 1911 all coronation and jubilee medals have been a standard 32mm in diameter. Campaign medals (GSM, South Atlantic, Gulf, Iraq etc) are a standard 36mm. Would therefore be a fair bet that the 2012 medal will be 32mm.
If HM died shortly before her Diamond Jubilee it's doubtful if the coronation would take place before 2013, and no reason to expect that the same qualifying service would apply - might be more sparingly issued, like the 1953 medal.