What makes a regular penny different from a penny made in the Denver Mint?

Answer 1

Actually, cents made at the Denver mint ARE regular pennies. Both Philadelphia and Denver make roughly equal amounts of cents each year.

Most US Coins today carry mint marks: P for Philadelphia, D for Denver, S for San Francisco (and even Wfor West Point). The mark indicates at which facility the coin was minted.

Until the 1980s, however, the only time Philadelphia used a mint mark was during the war years of 1942-1945, when it put a large P on the reverse (back) of the silver war nickels.

So any coins prior to then that did not have a mint mark were stamped at the U.S. Mint's Philadelphia facility (which as the nation's first and largest, felt it didn't need a mint mark on coins which it produced).

Cents are a special case, though. Even after 1980, cents made at Philadelphia don't carry a P mint mark. The reason is that when demand is high, the mints at San Francisco or West Point have been called on to make extra pennies. Because these mints are smaller they can't strike as many coins and the Treasury doesn't want to create "instant rarities", so those mints' coins are also struck without mint marks to blend in with the ones made in Philadelphia.

The notable exception to this is the rare 1922 Plain Lincoln cent error coin. All 1922 cents were minted at Denver, and were supposed to carry the D mint mark; but due to errors caused by the increased production demand, some 1922 cents were stamped with the mark apparently filled in, making it appear as though the coin had been produced in Philadelphia instead.