What is the value of a 1966 nickel without a mint mark?

A 1966 nickel without a mint mark is known as a Jefferson nickel and was minted in Philadelphia. Generally, its value is close to its face value of five cents, as it is quite common. However, if it's in uncirculated condition or has unique characteristics, it may be worth slightly more, typically ranging from 10 to 25 cents. For a precise valuation, consider consulting a coin dealer or reference guide.