I found this 1967 SMS quarter yesterday. It is the longest piece of wire I have seen struck on a coin. Also I have several 1966 and 1967 SMS that appear to be proof coins. Were these sets struck with proof dies?
Just for perspective reference, here is a 1965-P Lincoln Cent that was Struck Thru a piece of wire. Frank
My understanding is that the SMS sets that were made 1965-67 where struck with specially prepared dies, but they weren't proof dies. Some do have cameo effects though.