The 3 types refer to the reverse master hub designs. There were 3 different reverse designs used in 1972.
Type 1 low relief was used on all 1972 p&d coins from Jan. through Aug.
Type 2 high relief was a 1972 proof die used at San Fran mint that was mistakenly used at the Philly mint. Only one die was used.
Type 3 high relief was used from Sept. through Dec. New die steel strength is the cause of the 3rd reverse to be created. And was used for the rest of the years with the exception of the bicentennial reverse.
type 1 earth
type 1 eye
type 1 breast feathers
type 1 wing feathers
type 1 craters
type 2 earth
type 2 & type 3 breast and wing feathers. The feathers have been smoothed out and the raised lines at the edge of the wing feathers are gone.
type 2 & type 3 eye. The 2 lines above the eye are no longer there.
type 2 craters. The crater walls have been smoothed.
type 3 earth
type 3 craters. 2 small craters are inside the crater right above the L in dollar.
I hope this somewhat helps. Good luck with search.