It kind of depends on what the coin is and which TPG is grading it. PF is never used. But even with the same coin, an SMS Kennedy half, PCGS has been know to go 2 different ways, with SPxx being used and MSxx being used along with the SMS designation. NGC on the other hand usually uses MSxx along with the SMS designation. With later date SMS coins PCGS uses the MSxx with SMS while NGC uses SPxx.
For coins from 1965 - 1967 Special Mint Sets, PCGS used to use the prefix MS but now they use SP for "Special Strike". It would have made more sense if PCGS had changed the prefix to SMS (i.e. SMS65 or SMS66CAM), but that would have made to much sense. PCGS is also marking the 1998-S Mattie and the "satin Finish" coins from modern mint sets as SP "Special Strikes".
There were also some 1964 SMS sets...possibly given as presentation sets by the Mint Director (Eva Adams). I've read that there may be as many as thirty (30) of these sets made.
I was going to ask for some references supporting this, but I think your original thread at CU pretty much covers it: http://forums.collectors.com/messageview.cfm?catid=30&threadid=831502
For maximum confusion, couldn't you have gotten a 1965 set in MS-65, a 1966 set in MS-66, and a 1967 set in MS-67? :devil:
The slabs will be diferent depending on when the coins where graded. They changed how they marked them in the middle of the river.
I've read a variety of articles on the subject...none that I can reference at the moment, though. It seems logical that as the Mint was preparing to make coins with the SMS finish they would make some test strikes. It would also seem "plausible" that a political appointee such as Eva Adams might use that opportunity to create some 1964 SMS coins as presentation sets to her Congressional supporters. Especially in the immediate aftermath of the Kennedy assassination. Just because these sets may not have been an official release of the US Mint doesn't necessarily mean they don't exist. I would think (or like to think) that PCGS would have been very deliberate when coming to the conclusion that some 1964 coins they inspected were struck with the SMS finish. I agree that it would be nice if there was some sort of conclusive documentation to support a finding either way.
The coins designated as '64 SMS are like many other things in this hobby, we simply don't know and will probably never know, for certain, if they are indeed SMS. But NGC and PCGS both have designated them as such. http://coins.ha.com/c/item.zx?saleNo=346&lotNo=7926 http://coins.ha.com/c/item.zx?saleNo=1124&lotNo=2929 They base that designation on differences that the coins have from other coins dated '64 and similarities the coins have to the '65 SMS coins. There is little doubt the coins are different, they are their own evidence of that. But are they really SMS ? We don't know, either way. edit - one thing that might be worth noting. NGC and PCGS both have mistakenly designated a few '65-'67 coins as being SMS coins, when they were not SMS coins. Once the coins are removed from the original SMS holders, it can often be all but impossible to determine if they are, or are not, really SMS. The exceptions are the cameo examples.
ROFLOL When has NGC ever classifed this things as 1964 SMS? It has never happened. Long live the "myth".