I have seen these in a number of catalogs and on the internet, but they looked easy to make....and yes, they are easy to make.
Step 1: Dome Out the Coin
This is a doming block (from harbor freight tools) that is one of those tools that you use very rarely, but when you need it, it is essential.
I typically use a quarter when I am building these conchos or buttons, mainly because I like the designs on the state quarters. My favorite are Texas and Wyoming.
It is a simple as putting the coin in the doming block, taking out one of the punches (largest possible) laying it on the coin, and whacking it with a hammer a few times. This quickly turns the quarter into a nice dome shape.
Step 2: Solder on the Backing
I have a couple different devices that I connect on the back:
Each has a different use and ability to be removed.
Snaps: temporary as expected
T-nuts: semi permanent (screws will stay in)
It is a matter of laying the device in the cup side of the coin and soldering it in. I have also used silver solder, definitely stronger, but you do need higher heat. With the solder, a small butane torch did the trick.
Step 3: SNAP Backing
Here is the coin and the snap hardware soldered on and the actual snap pressed on.
Step 4: Buff and Polish
With any of these methods, the coin gets discolored by the heat, but a quick buff with a polishing wheel and it looks great.
I have used these on leather guitar straps, belts, or other leather crafts.