The US never struck any coins in lead. Only in 1943 Lincoln cents were struck on Zinc coated steel planchets because the copper was needed for the war effort.
In general, "S" mint marks from the San Fransisco mint are more scarce than other mint marks when it comes to pennies. But just because it has an "S" on it doesn't make it a rare, or even scarce coin.
Coins made at the Philadelphia mint did not have mint marks until the 1980s. Your coin was made at the Philadelphia mint.
They were minted at the Philidelphi(no mint-mark), Denver(D) mints. These pennies are not rare.
If you're referring to U.S. pennies, the mint mark is located just below the date, just as it's been since the Lincoln cent was introduced in 1909.
Any Lincoln cent that does not have a mintmark was struck at the Philadelphia Mint
In 1942, At the Philadelphia mint there were 657,828,600 minted for circulation, and 32,600 proof pennies minted. At the Denver mint there were 206,698,000 minted. At the San Francisco mint there were 85,590,000 minted.
Pennies are minted at three locations in the US; The San Francisco Mint, The Denver Mint and the Philadelphia Mint. Pennies from San Francisco have an "S" on them. Pennies from Denver have a "D" on them and pennies from Philadelphia have no letter.
In 2011, the U.S. Mint produced 4,938,540,000 pennies.
1974 was the last year the San Francisco Mint issued Lincoln cents for general circulation.
The year was 1974 for circulating coins. Proof coins still have the "S" mint mark. Technically speaking, the United States never issued "pennies" - unlike Great Britain, they are referred to as "cents."
Company that makes pennies
Australian Pennies from 1955 to 1964 inclusive were minted at either or both of the Melbourne Mint and the Perth Mint. Pennies minted at the Melbourne Mint have no mintmark. 1956 Pennies minted at the Perth Mint can be identified by a dot "." after the "Y" in PENNY, eg. "PENNY.".
At the Philadelphia Mint.
Company that makes pennies
1938 IN a MINT
Australian Pennies from 1955 to 1964 inclusive were minted at either or both of the Melbourne Mint and the Perth Mint. Pennies minted at the Melbourne Mint have no mintmark. Pennies minted at the Perth Mint can be identified by a dot "." after the "Y" in PENNY, eg. "PENNY.". In other years, Perth Mint Pennies can also be identified by a dot after the "A" in AUSTRALIA, eg. "AUSTRALIA." or, a dot between the designers initials "K.G".
Australia struck pennies in 1955 at two locations - the Melbourne Mint and the Perth Mint. The Perth Mint pennies have a very small dot, to the right and in line with the base of the "Y" in "PENNY" on the reverse / tails side. The pennies struck at the Melbourne Mint do not have this dot.