Cam across a how to make a ring video and watched a few more. Interesting. Seems easy enough if you have patience for it.
This guy makes and sells his items. I guess most of them do. He has a few tools that make like easier and the results better.
This was the first one I saw. He has done this without special tools to show it can be done with basics, although he does have better tools as well.
I wouldn't mind one of these. I can't think of any Australian coins I would want to make one from but plenty of US coins. the first guy has a web site with some nice examples. A JFK coin, some walking liberties of course and a few others. Morgans.