Well, from 1965-1967, struck coins had no mintmarks, and many of them were minted at the San Francisco Mint. One reason was that the director of the Mint at the time was unfairly blaming coin collectors for hoarding certain mintmarks with lower mintages. Plus you had a coin shortage as people started hoarding silver dimes, quarters, and half dollars right before and after the changeover in 1965 as the value of silver for each was worth more than their minted value. (Mintmarks not only returned in 1968, but the mintmarks were moved from the reverse of coins to the obverse.) Coins from 1965-1967 were also not released as proofs or in Mint sets in the regular sealed packaging, but the Mint started to release "Special Mint Sets" (or SMS) for those years in hard plastic packaging. These coins also had a different finish; shinier than business strikes but yet not proof and struck with more die pressure. This is why these coins typically look better than average compared to other years when found in pocket change or couch cushions of fat people everywhere.
How does the dealer (weinberg?) Know that it was minted in S.F. ????? All i see is a sticker on the bottom of the slab. PCGS notated the coin as 1967 only
I saw on a thread some months back that the Chinese copy houses are actually producing copies of the dime on a 16 penny nail thing.