The obverse of the IKE did not change over the eight years of issue but the reverse of the IKE dollar when through five different changes. Three of the reverse die changes was in 1972. They are noted as Low-relief (Variety 1), High-relief (Variety 2), & Improved High-relief (Variety 3).
The Low-relief (Variety 1) reverse die has a flattened Earth and three islands off of the southern and eastern coast of Florida and was used for both the uncirculated copper-nickel and silver coins of 1971 and most of the copper-nickel coins of 1972.
The High-relief (Variety 2) reverse die has a round earth and weak or indistinct islands. It was used for all 1971 proof coins and all silver issued 1972, and the reverse of some 1972 Philadelphia copper-nickel. The 1972-P Variety 2 copper-nickel issue is very scarce.
The Improved high-relief (Variety 3) reverse die were used on all late 1972-P issued copper-nickel coins and for all subsequent issues. The islands on the Variety 3 die are off the southern coast of Florida.