SMS=Special mint set, plus some history

Back in 1965-67, the mint made what they called special mint sets. Proof sets were not made for those years. Mint sets are assembled from normal business strike coins. These coins are struck once under standard minting pressure from the dies. For the special mint sets, the coins were stuck once like business strikes, but under higher pressure. Overall, they had a nicer look than the regular business strike.

For 2005, the mint changed the way they make the mint sets. The coins have a satin finish unlike the normal 2005 business strikes being released for circulation. PCGS is labeling these coins as satin (SF) on their holders. NGC is labeling them as SMS for special mint set on their holders.

You can also find 2005 coins with just the MS grade on the holder. These are the normal business strikes for 2005.