I would think due to the higher grades available (like there actually available, LOL) these were saved by people that knew what they had, mostly MS65 & MS65 coins survived, and they seem to have been well taken care of, especially fro the time era, no details, no cleaned, etc.
"Buy the Book Before You Buy the Coin" - Aaron R. Feldman - "And read it" - Me 2013! ANA
Life Member #3288 in good standing since 1982, EAC Member #6202, NBS Member, 2¢ variety collector.
See my want page: http://goccf.com/t/140440