What is the value of a 1941 us copper nickel?
What you have is probably a normal alloy nickel that has discolored over time (the coin actually contains 75% copper). A true mint error where the nickel was minted on an incorrect planchet or blank could be worth from maybe $20-100 on up, depending on condition, but these are very rare and must be authenticated by a reputable grading service such as NGC or PCGS.
Please don't assume that because a coin is old it has to be made of silver. It's made of copper-nickel like all other nickels except the WWII ones with a large mint mark above the dome of Monticello. 1941 is not a rare date for Jefferson nickels. There's more information at the question "What is the value of a 1941 US nickel?".
If you have a US nickel, it is either coated with copper or has changed color due to exposure to some chemical and has no special value. If it is a 1942 Canadian nickel, it varies from $.40 to $1.75 in circulated conditions, $3 and up in uncirculated grades. The material is called "tombac" and is an alloy of copper and zinc.
To clear things up, 1941 nickels aren't war nickels. The US didn't enter WWII until December of that year, and war nickel production didn't start until 10 months later. All 1941 nickels were struck in the standard alloy of 75% copper and 25% nickel, so a copper-colored coin could result from exposure to heat or chemicals. In particular, nickels are often copper-plated in high-school chemistry experiments.
8-22-11>>> The only US nickels to contain any silver are the "War-Nickels" that were struck in 35% silver from late 1942 through 1945 and can be identified by the large mintmarks above the dome of Monticello on the reverse. Please see the question "What is the value of a 1941 US nickel?" for more information.
All US nickels except the famous "war nickels" from WWII are made of 75% copper, but the remaining 25% of the alloy that's nickel is enough to give the coins a silvery color. The only way a nickel could appear copper in color is if it were tarnished, altered by exposure to chemicals, or plated as part of a high-school chemistry experiment (we made lots of them when we studied half-reactions!). Regardless of the cause…