When the die moves post strike, the die itself slides/moves and alters the freshly struck coin.


Sometimes it bounces and affects the devices higher up, sometimes even on the tops of devices, only affecting those higher areas.


This is never a doubled die. A double die coin is formed by hub doubling on the die creation process.
Machine Doubling is a striking issue. You can have
Machine Doubling on a doubled die or a normal die.


But a doubled die coin is only struck by a hub doubled die. (A doubled die is a die issue, not a striking issue)
Do you know where to look at on the devices to tell the difference?
Machine Doubling affects the outer edges of one side of the devices.

A bumps/pushes and removes the normal contour of the devices. The affected area will look flat. Or raised where the metal was pushed aside.
https://imgs.inkfrog.com/pix/coop49...GHER_AAB.jpgOften shiny on new coin, as light reflects stronger on flat devices. But they are not doubled dies, just altered strike coins from the dies movement post strike.

On a doubled die, the devices will be larger/taller on the center edges of the devices.

The closed devices will actually have smaller openings because of enlarged devices:

Notice these two images. The top one is a normal die coin. The lower one is a doubled die. What creates a doubled die. During die creation, the movement/location of the hub enlarges the devices on the die.


Thus the coins struck by that die will show the hub enlargement on the coins.

Thus the devices will be wider in the center areas of the devices.


And the closed devices will show a smaller area. (note on the coin on the 'Q' 'D' 'O', the centers are smaller)


So now that we know what to look for. What not to look for:
1. Don't look at the
outside edges of the devices for a doubled die. On that area you will find
Machine Doubling and extreme die wear. So look at the centers of the devices, not on the outside edges of the devices.
2. If you see a 90 degree angle on the outside edge, that is
Machine Doubling.

3. If you see a distorted outer edge of the devices that is die wear.

Die wear is always on the devices that are closer to the edge of the rim area on a coin.

So if you don't see enlarged devices on a coin on the centers, move on to the next coin.

To continue to look for something there, guess what you will find.
Machine Doubling and die wear. Why waste time on
Machine Doubling and die wear looking devices. It is there, or it isn't. If you don't see it, move on. If you question it, set it aside and move on to the next coin. The time over spent on a coin, maybe holding you back from finding a worth coin. Hope this helps.
Another way to learn what to look for is to check out the sites and figure out why they are listed as doubled dies.
For cents only on this site:Coppercoins.comhttps://www.coppercoins.com/For all denominations check out these sites:Variety Vista:http://www.varietyvista.com/index.htmDoubled dies: John Wexler's site.http://www.doubleddie.com/1801.htmlBy studying this, is training your eyes as to what to look for on a doubled die. Soon you will figure this out and soon be finding the real keepers and avoiding the speed bumps.
CoopHome:
How can you tell Machine Doubling from a doubled die? know which is which will save you a lot of time. or you can continue not finding doubled dies? your choice.