I'm afraid the answer is "Yes, no, and maybe." It depends on the year of issue and the condition of the coin.
Since the 1940s the Denver Mint has turned out about as many cents as the Philadelphia Mint so D-mint cents from the last 70 years or so aren't generally scarce. You have to go back to the early 1930s and before to find some that are worth any reasonable amount.
As for San Francisco, at one time that Mint was active almost on a par with Denver and Philadelphia, but some years it in fact did mint fewer coins than the other 2 facilities. Also there's a bit of an "air" about S-mint cents because they haven't been struck for circulation for decades and are thus comparatively unusual in most peoples' experience.
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Generally, coins are valuable because of the price of the metals they are made from, but if you mean in a collectible way: One thing that makes a penny valuable is the date. They older the coin usually the more valuable. Another thing is the mintmark. For example 1943 pennies with a "S" mintmark are more valuable than pennies with no mintmark. Another thing is the condition of the coin. The less ware it has the more it's worth.
The most valuable ones are the 1943 copper penny, and the even more rare 1944 steel penny.
It is worth 1 cent unless it carries the mintmark "S".
It depends on the mintmark and condition. A 1928 penny with no mintmark (thus minted in Philadelphia) in not that great of condition might only be worth $.10, however if it has a D (Denver) or S (San Fransisco) mintmark it could be worth a dollar or so in the same grade. If you have a perfect example it can range anywhere from $90-3,000 depending on the mintmark, but those are only for the absolute best coins, if you picked your coin out of circulation on average it would be worth $.10-$.20 with no mintmark and I'd estimate about $1-2 if it has an S or D mintmark.
2009 pennies were made in mass productions. Currently a 2009 penny is only worth a penny unless it is a proof. If it is a proof it will have the mintmark "S" below the date.
Generally, coins are valuable because of the price of the metals they are made from, but if you mean in a collectible way: One thing that makes a penny valuable is the date. They older the coin usually the more valuable. Another thing is the mintmark. For example 1943 pennies with a "S" mintmark are more valuable than pennies with no mintmark. Another thing is the condition of the coin. The less ware it has the more it's worth.
No they are not, in general just because a coin has a mintmark does not make it more valuable.
There is no mintmark on the 1921 British Penny, they were all minted at the Royal Mint London.
Usually S mintmark wheat pennies are worth more.
A mintmark is a small identification mark used to tell which mint it was made in.
The English/British One Penny coin has been issued for over 1,100 years. All years of issue of the British decimal New Penny and Penny are still potentially in circulation so, unless they are part of a Proof or uncirculated mint set or are individual Proof or uncirculated coins and in absolute mint condition, they are worth 1 Penny. 20th century predecimal Pennies would need to be in mint condition to attract any significant value. The most spectacularly valuable example would be the 1933 Penny. There are 7 known coins. Other than that, there would be the - 1919 (KN mintmark & H mintmark), 1918 (KN mintmark & H mintmark), 1909 (variant - 1 directly above tooth) 1902 (variant - with low tide - further done Britannia's shin)
underneath the year
It will have a S mintmark.
The mintmark is very clear compared to the type-1, that's why it's more valuable.
An Australian Penny or Halfpenny with a "Y." (PENNY.) mintmark indicates that the coin was minted at the Perth Mint. An Australian Penny or Halfpenny with a "I" mintmark indicates that the coin was minted at either the Calcutta or Bombay Mints in India.
Philadelphia. Cents (pennies) from the Philadelphia mint have never carried a mintmark.
The 1922 Australian Penny does not have dots. The incredibly confusing system of dots above and/or below the scrolls was used as a mintmark to distinguish between coins minted at the Sydney Mint and the Melbourne Mint in 1919 and 1920.