1968-S LMC RPM Or Something Different?

But the outside edge is part of the normal mintmark is what you are seeing. The Machine Doubling is a very thin line that is between the with white and yellow arrows. That is how slight the Machine Doubling is. But it gives the suggest that there is a part of a RPM. But is it pushing the metal SW towards the direction of the MD.When you isolate the outside part of a mintmark and consider the push of the Machine Doubling, that you are seeing, on this image. Note the same thing is happening also on the date as well. That tells me the machine is making this difference and all other examples of this die, will not be showing it. Just this one machine doubled coin. This would never be listed as it is the only one like it. If is not a die variety, but just slight Machine Doubling.

1968S-1MM-001

Evidence of a second punching is needed to be a RPM
This one is a north. You can see it on the top of the mintmark and in the lower loop of the 'S'.

1968-S RPM-002
http://www.varietyvista.com/02b%20L...8SRPM002.htm
S/S West on this one.

1968-S RPM-003
http://www.varietyvista.com/02b%20L...8SRPM003.htm
Note this one is just showing a slight spread to the SE.

Its not the enlarged mintmark, that makes it a RPM, but evidence of two punches.

Look at the size of the Mintmark? It is not a RPM. It doesn't show a second punching. The punches enlarged the mintmark, but doesn't show a separation of the punches.

If you found this in an original roll of cents, check to see if you can find another one with the same mintmark location. Then you will know that is Machine Doubling, when you see the same markers on another coin with the same mintmark location.