According to PCGS they define SP as
Quote:
Specimen (SP) â€" struck well like a Proof, but with a satiny, sometimes matte, semi-granular looking
The satin proofs, some of the coins out of the special mint sets in the 60s, the 5 oz ATBs, and some canadian coins are the ones I can think of off the top of my head that have gotten the SP. It confused the heck out of me at first when I was looking for my
Presidential dollar for my graded type set seeing satin 68s cheaper than ms 67s