According to Breen, the high relief eagle (Type II) is only seen on proofs in 1957 and the low relief on business strikes.
in 1956, Type I on business strikes and 5% of proofs, Type II on 95% of proofs
in 1958, Type I on business strikes and Type II on proofs and 20% of business strikes.
But for 1957 if the eagle is in high relief and there are three feathers left of the perch, then it must be a proof.
gormang