July 5, 2009 In 1955 there were 3 US mints in operation. One was in Philadelphia, one in Denver and one in San Francisco. The Denver mint has the letter "D" under the date on the cents made there. The San francisco mint has the letter "S" under the date of the cents made there. The Philadelphia mint does not put a mintmark under the date of cents made there. So if you have a 1955 cent and there is no "D" under the date, then the coin was minted in Philadelphia. These coins are fairly common and even in uncirculated condition they can be bought for about $3. Circulated coins can be bought for as little as 3 to 5 cents each.
A lot
The mint mark is not "missed" or even missing. Cents struck at Philadelphia don't have a mint mark. Those struck at Denver have a D, and an S stands for San Francisco. Unless you have an obvious "double die" 1955 cent (with a second, ghost-like image rotated about 2 degrees) you have an ordinary coin from Philadelphia worth only a couple of cents in average condition.
If it shows any wear value is 5 to 25 cents
The US hasn't ever used a B mint mark. Please see the Related Question for more information about 1955 cent values.
Numismedia quotes a retail value of $900 to $1500 depending on condition.
Most 1955 cents are not rare and are only worth about 3 to 5 cents to a collector. The only rare variety is the double-die cent that clearly shows two images on the front, slightly offset from each other. These can be worth $900 to over $2000 depending on their condition. See the link below for a picture.
The 1955 Doubled Die cent is a die variety that occurred during production of the Lincoln cent at the Philadelphia Mint in 1955.
Retail for circulated coins is 5 to 15 cents. Excellent uncirculated examples are under a dollar
one cent
1 cent Please check your pocket change. You'll see many cents dating back to at least the mid-1950s. Except for a 1955 double-die error cent, all are worth face value only.
Value of 1986 fifty cent piece
It is 1 cent!