In 1951 there were two designs on the reverse of the 5 cent coin. The first is normal beaver issue but struck on chromium plated steel due to the need of nickel for the war effort. There was 2 varieties of this issue, a low & a high relief obverse with the high being the rare issue. The second one commemorates the 300th anniversary of the isolating and naming of the element nickel, and was appropriately minted in nickel. The design on the reverse depicts a nickel refinery.