Royal Engineers WWI medal

A few bits of research have come to a conclusion over the last day or so. This one has a international connection as well as a local one for me.
I received the WWI Victory Medal awarded to 46124 Charles Henry Hutton Black of the Royal Engineers from Jan C of Canberra. How this medal came to be in Australia is a mystery.
Other than Black's Medal Index Card there was only one other reference to him that I could find. That was on Ancestry.com and a family tree owned by Andrew V who is Black's great grandson.
Andrew lives in Scotland which makes the mystery of how the medal ended up in Canberra even more interesting.
The returned medal tally is now 1717.