No reason they shouldn't be real. There were over 2 billion minted in Philadelphia that year which will not have a mintmark.
Those Lincoln-Kennedy cents were modified by a private company, NOT the U.S. Mint. To find the value, check how much they're selling for on eBay. It's probably not much.
1974 was the last year the San Francisco Mint issued Lincoln cents for general circulation.
The mint mark position on all Lincoln cents is the same - under the date. No mint mark - Philadelphia "D" - Denver, beginning in 1911 "S" - San Francisco, 1909 to 1955, 1968 to 1974
The "S" mint mark is used by the San Francisco mint and is located just below the date on the 1941 Lincoln cent.
No mint mark10 to 75 cents for a circulated coin, $1.25 to $31 uncirculatedD mint mark10 cents to $1 for a circulated coin, $4.50 to $35 uncirculatedS mint mark12 cents to $1.75 for a circulated coin, $4.50 to $27 uncirculated
When you see this in ebay ads and so forth it means "Mint On Mint Card. So the car is in mint condition and the package is in mint condition.
If you mean How much is a 1928 Lincoln cent in Mint State condition. Reatil is $10.00
eBay is a good place.
In mint condition it will be silver.
If it's after the 1950s with an S mint mark, that makes it a proof coin. A '68-S might be worth a dollar or so as long as it's still in mint condition. Not all S mint 1968 Lincoln cents are proof. The San Francisoc Mint made business strike Lincoln cents from 1968 thru 1974. The 1968-S Lincoln cents released into circulation are considered common and still found in circulation today. Uncirculated examples are less than a dollar.
July 3, 2009 A Complete P and D 1974 US Uncirculated Mint set can be bought for about $6 to $8.
Any Lincoln cent that does not have a mintmark was struck at the Philadelphia Mint