We now know that Chivers' medals went missing 40 years ago when the tin they were kept in was mistakenly thrown out during a house move. Where this medal has been for all those years is unknown, however, it has lived a hard life. It is now very dull compared to other examples and the surface is quite pitted. As can be seen in the pictures, the image of the King and the naming are quite hare to distinguish.
The returned medal tally is now 666.
Added 3 Jul 10.
I have recently received this photo of Chivers from his family.