1964 Lincoln Proof It Could Be SMS

Agree. Proofs can vary dramatically from set to set. Specialists do well cutting up proof sets and holdering top grade cameo examples before 1957 especially.

I have noticed, on some of the mint sealed coins I have, that the plastic tends to get milky which may explain the difference of appearance of what's inside.

There is but it is extremely rare and it is said that all the examples that were made are accounted for

Finding a 64 SMS trial strike is difficult. When these were produced, most of the sets were retained together as these usually sell in groups in big auctions. One of the key attributes is you'll notice the same file lines as what you would typically see on the 65-67 SMS coins. A 64 SMS nickel just recently sold for big money in the last week or so.

here is information from a web site:
http://www.PCGS.com/News/1964-Speci...nt-Set-Coins
[quote]
Currently the PCGS Population report shows 22 Lincoln cents, 18 Jefferson nickels, 22 dimes and 28 Kennedy half dollars graded as 1964 SMS. Some of these population figures may be inflated since some of the coins may have been cracked out and resubmitted in hopes of an upgrade. However, even if the population figures were close to the actual coins in existence the supply would be extremely limited compared to their popular demand. [/img]
So to imagine finding them in circulation would be very, very, rare. 22 cents out of 2,648,575,000 cents from Philly that year. Pretty slim odds.