The 1968-S Lincoln Cent is really common in circulated grades all the way up to MS66 grades. In MS66 condition it is not as common but there are plenty of examples out there to meet the demand. Examples that are really high end MS66 are much more difficult to locate. In MS67 condition it is scarce with less than a hundred examples known. There are a few examples that are really nice for this date that almost look proof-like but those are the diamonds in the rough and worth keeping an eye out for, as they tend to bring similar prices to non proof-like coins from this issue.