This is the first year in which Roosevelt Dimes were produced for circulation. The Mint struck 1946 Dimes at three different Mints this year. The 1946 Dimes were produced at Philadelphia, Denver and finally at the San Francisco Mint. Out of the three Mints, San Francisco produced the least by far, as it only struck 27,900,000 coins this year. Compare this to the mintage of the 1946-P Roosevelt Dime with a mintage of 255,250,000.
For the most part the 1946-S Roosevelt Dime is considered common in most circulated grades and even all the way up to MS63 grade or so. In MS64 they are somewhat scarce but with enough searching you can buy the coins with minimal effort and at a small premium from silver melt values. In Ms65 condition they are a little scarcer but still somewhat easily located at a small premium. In MS66 condition they become scarcer with a couple thousand examples known. Many examples are still uncertified. In MS67 condition they become a challenge to locate and possibly about 500 -1,000 examples exist. In MS68 condition they are almost unheard of and there are probably no more than 2 dozen known.