Please explain.

[RyanAsberry]

Is this the cause of machine doubling?

[DWLange]

Yes, and it's very common on S-Mint cents 1968-73. NGC uses the traditional term "Strike Doubling," and we get many such coins that submitters believe to be DDOs.

[JKK]

Good spot. That shelflike look is very indicative of mechanical doubling.

[Conder101]

Not the CAUSE of Machine doubling, the RESULT of it.

[amk1113]

Yes, this is the result of double striking, and often happened from 1940 onward. you hear of all these double strikes, whether on the entire obv., or as small as the double die on themint mark, but its definitely from the mint. an error that isnt so uncommon actually, but is really cool.

 

cheers!

[Conder101]

Not from double striking but from the die shifting during the strike or while retracting. (frankly I'm not sure which)

[Mohawk]

10 hours ago, Conder101 said:

Not from double striking but from the die shifting during the strike or while retracting. (frankly I'm not sure which)

I remember reading somewhere years ago in one of the coin magazines that both of those can cause machine doubling.  I wish I could remember the exact publication, but this was probably 15 years ago.