The Mint produced Proof Wheat Lincoln Cents from 1909-1916, then again from 1936-1942 and finally from 1950-1958. From 1950-1958 Proof Lincoln Cents, the 1956 Proof is one of the more common dates as it has one of the higher mintages. As far as condition examples in PR63 to about PR68 are really common. With the Cameo designation this date is uncommon in PR67 and higher. with a Deep Cameo designation it is scarce in any grade.