First, the legal stuff. Most interpretations of the statutes applicable to defacing coins in the U.S.A. are applied to mean if you deface currency for fraudulent purposes. Such as turning a 1.00 dollar bill into a 10.00. Which is why there are so many penny pressing machines in your local tourist attractions. In other countries, the law varies. These buttons are not being made for fraud. They are nice, primitive buttons that can be used to a nice effect in sewn, knit and crochet projects. For more information, check out this site here.
At the time of this writing, copper pennies, that is, 1981 and earlier, are worth 3¢ each. Copper keeps rising in price. So I'm in the habit of checking all my pennies as they come in and separating out the copper ones. This is also a good idea if you're pressing pennies in penny machines. That way you'll have a piece that's nearly all copper!
To make these is so simple. Using a bench block or similar surface, a hammer, and a metal punch they work up very fast. If you want very shiny pennies, you can shine pennies with a bit of ketchup. Really truly! Or vinegar and some salt, or even toothpaste.
I like the rough way these look. I have my husband hammer them flat very quickly and he hits at odd angles and mars up the surface a bit. With more deliberation they come out rounder without the scars from the hammer, like the buttons on the apple cozies above. I polished the pennies before hammering them and I was fairly careful how I hammered them. So they turned out very smooth and a bit shinier.
So, you put the penny on the block, and hammer it flat. Then comes the fun part. Punching the holes.
Using this two-hole metal punch from Rings and Things, put the flattened penny in throat for the smaller hole. The throat on the smaller side of the punch is deeper than the throat for the bigger hole. Then you screw down the punch and it punches out a little hole. This works very easily, you don't need much strength at all to twist down the punch. Pull the penny out and reposition it to punch the second hole. For mine, it worked perfectly to put the edge of the penny all the way to the back of the throat then punch a hole, then for the other side, just turn it around and put the opposite edge against the back of the throat of the punch.
Rings and Things also carries the bench blocks, more professional hammers than the one I used, and dapping blocks that could be used to make a more domed button. The also carry lots of copper shapes and sheet copper if you don't want use a penny.
The two-hole metal punches can also be used on pressed pennies to make pendants or keyrings of them.