I have a little to add to the medal made by the soldiers.
My father was a "RAT"in the 13th Field Co. I still have his medal (see attachment)which is numbered 500.
The first letter of the serial number indicates the state they enlisted. In my father's case it was Queensland hence QX and FP Bingham would have enlisted in Tasmania. My father, who died in the sixties, like most in that time spoke little of his time in Tobruk. However, I do remember him saying that this was not his original medal. He said he had some involvement in the making of the medal and originally had one of the early numbered medals. Damian Lewis's reference to the field engineers making the medal, gives some credibility to my father's account, as he was a Sapper in the field engineers.
The medal is a very treasured item for me, and I am pleased to see article recording some of the history of the unofficial medal.
Below are the images Col supplied. Thanks! Below that, for comparison, are the images of the previously-discussed medal.