The current US mint marks are:
P for Philadelphia
D for Denver
S for San Francisco (for proof coins only)
W for West Point (for commemoratives and gold only)
Until recently most coins from Philadelphia did not have a mintmark so you may find many older coins lacking mint marks. Dates for the P mint mark are:
> 1942-45 : "war nickels"
> 1979-present : dollars
> 1980-present : nickels, quarters, dimes, halves
Philadelphia cents do not have a mint mark, even after 1980.
Mint Marks on Older CoinsS for San Francisco on circulating coins 1854-1955, also some nickels and cents 1968-74C for Charlotte, NC 1838-1861
CC for Carson City, NV 1870-1893
D for Dahlonega, GA 1838-1861
O for New Orleans, LA 1838-1861 and 1879-1909
Mint marks only appear on coins. US paper money is printed by the Bureau of Engraving and Printing, while coins are made by the US Mint. They're completely separate operations. When silver certificates were issued the BEP had only one facility, in Washington DC. Any small-size bill you may have was printed at that location.
If a penny has no mint mark, it typically means it was produced by the Philadelphia Mint. Mint marks indicate where a coin was minted, and coins from the Philadelphia Mint, the oldest U.S. Mint facility, do not have a mint mark.
US Coins with no mint mark were minted at the US Mint's main facility in Philadelphia, Pennsylvania.
The mint is the facility where it was made, so I assume you're referring to the mint MARK, which is the letter that indicates the facility. The mint mark position on a 1909 Indian head cent is on the back under the wreath. On a Lincoln cent, it's under the date. Most 1909 cents were made in Philadelphia so they don't have mint marks. Only a relatively small number were in San Francisco, and they carry an S mint mark.
The letter on quarters represents which mint facility produced the coin. "P" stands for Philadelphia Mint and "D" stands for Denver Mint. These marks help identify where the coin was minted.
The US mint did not use mint marks on the 1965 half dollar coin.
The Related Link below has a list of dates, mint marks, and mintage totals.
None of them will have mint marks.
About $1.30 to $1.50, depending on the condition and mint marks.
The "Crown" and the "Castle" are two of many mint marks types indicating where the item was made or minted. The Mint Marks are many and varied. There are at least three different "Castle" mint marks and two different "Crown" mint marks. Other mint mint marks include crosses, stars, flowers, moons, keys, animals, etc. all of which have many variations, and these are only the British marks.
Please check your coin again and post a new, separate question. The US has never used an E mint mark. The only mint marks on cents were "S" (San Francisco) and "D" (Denver). Philadelphia cents don't carry mint marks, even today.
Bills don't have mint marks. The U.S. Mint only makes coins. Bills are printed by the Bureau of Engraving and Printing, which has only 2 facilities. The main plant in Washington DC doesn't put any special designation on its bills. The auxiliary facility in Fort Worth marks its bills with a tiny "FW" next to one of the plate designators. It may be in different places on different bills so you have to look closely for it.