Need Help With This Item... 1991 LMC DDO?

Kind of hard to say without a picture.

I was thinking the S and you in trust?

to the CCF!

Machine Doubling happens after the strike. The die struck the coin and bounced after the strike/or the machine was loose and damaged the strike coming up from the strike. It varies on how high up this can happen. On proof coins it can move the devices from the bottom of the coins devices. Often call flat field doubling:






Because the proof coins are struck more than once, this can happen on them. Another form of Machine Doubling, called Machine Doubling as the coin was altered by the machine after the strike.
There is also classic Machine Doubling often seen on many coins:


Note on this example the strength varies from each device.


Note on this example how the strike shoved/distorted/moved the devices shape after the strike. It reduced the sizes of the devices. Nothing is doubled, it is actually reduced in size.


Because this MD is caused by the machine, it alters the devices. This is very common to find on some years. On the 1968-1972 years it is very common to find. Even doubled dies can be affected with Machine Doubling altering them:

Note the lower image. This is a doubled die, but the devices were altered a bit from the machine damage after the strike. (note black arrows on image above)
A doubled die is just as the term says. The hub doubling is on the die. So Machine Doubling is caused by the machine and can affect doubled dies. But most often the MD happens on regular coins, altering them. While they look interesting, they are not varieties. They are a striking issue.
coophome= Machine Doubling