I found out when I was doing my IKE set that type 1 came out of the 1975 mint and proof sets, and type 2 came out of 1975 mint and proof sets, because both years had the same date 1776-1976. with that said there was different types 1971 or 1972. but on blank planchets I don't know, I'm still to new at this
I forgot to mention, that the lettering was different, that also made it type 1 or2. hope this was helpful