Really nice examples of Machine Doubling. Any time you see doubling on both the date and mint mark for pre 1990 coins (your 1968-s example), it is a sure sign of Machine Doubling.
The shelf like appearance of the doubling is also a dead give away. Try to compare these examples with photo's of true doubled dies and you can start to learn the differences.
The shelf like appearance of the doubling is also a dead give away. Try to compare these examples with photo's of true doubled dies and you can start to learn the differences.























