There are two different Jefferson nickels dated 1942. One is made from 35% silver with a large "P" or "S" mintmark on the reverse over Monticello. This is a War Nickel that's worth about $1.00 in circulated condition. The other is a common copper-nickel coin that in circulated condition is really only worth face value.
It's the usual practice of this site to answer a single question at a time. Please see:"What is the value of a 1940 US nickel?""What is the value of a 1942 US nickel?""What is the value of a 1944 US nickel?"
There is no such thing as a Mercury nickel. See the related question below.
In 1942 silver nickels were only minted at Philadelphia and San Francisco.
No such coin exists. All 1942-D nickels are made out of the standard 75% copper 25% nickel. Only 1942-S and 1942-P nickels were struck out of the "war nickel" alloy of 35% silver. A 1942-D nickel is worth about 7 cents if circulated and a couple of bucks if in better shape.
The last buffalo nickels were struck in 1938
The large "P" above the dome means it's a "war nickel" that is struck in 35% silver. The nickel was removed for the war effort and silver was used as a replacement, this was done from 1942 - 1945. Because it has a small amount of silver the value is about $1.00. NOTE: The 1942 war nickel is the first US coin to ever use a "P" Mintmark.
If you mean a Jefferson nickel dated 1942-1945 with very large mintmarks on the reverse, the silver value is about $1.00. They are 35% silver.
Most are only face value but some can be worth $1.00-$5.00 it depends on the condition of the coin.
1942 Canadian Five Cent Nickel (KM# 33) OBV: George VIREV: Facial Value Above BeaverComposition: 99.9% NickelWeight (g): 4.54Diameter (mm): 21.20Mintage: 6,847,544
The only years silver was used in US nickels was 1942-1945, the coin is face value.
Your nickel contains no silver. Only nickels made from 1942-1945 contain silver. See the related question below.
All nickels except "war nickels" from 1942-45 are made of copper-nickel, not silver. What you have is an ordinary coin worth 5 cents.