Note when you compare the Machine damaged - Normal - Doubled dies side by side.

1. Machine damage on a coin reduces the overall shape of the device.
2. The normal one is the same overall size if the MD example, but the device is not reduced from the MD, just a normal coin.
3. Note the hub doubling on a doubled die. You see two devices or enlarged from the hub doubling.
Machine damaged coins are from a normal die and while the strike happened the machine caused this to happen. On a hub doubled doubled die, all coins struck with that die will show the same exact doubling. On MD coins they may vary from strike to strike:

Note these coins came from the same dies on the same run. Note how they are different?
Machine damage reduced the normal strike on this coin.

More MD strikes:



Note the "O" on OF? Note the reduction that the machine damaged cause on this device. Machine damaged coin are plentiful. Doubled die coins are harder to find.