A couple added to the stable. I bought the 93-O and 06-O in Baltimore. I once owned the 06-O before and didn't even realize it until later. No wonder I liked it so much. The 06-D was a recent Ebay purchase.
1839-0 50c NGC PF 64 CAC 1 of 4 or 5 made in New Orleans like me . Why do you think they would have made only 4 Proofs ? Very little information available . What's the difference between a Special and a Proof?
Here is what my ebay bucks bought, a Augustus provincial with Rhoemetalces I, but the scarcer 4 head with Livia, Augustus wife. KINGS of THRACE, Sapaian. Rhoemetalces I, with Pythodoris, Augustus, and Livia (Late 1st century BC-AD) Æ 27 O: Heads of Augustus, laureate, and Livia, conjoined right; to right, capricorn right, holding globe. R: Diademed head of Rhoemetalces and draped bust of Pythodoris, conjoined right. 27mm 13.8g Youroukova 182-4, 186; RPC I 1708
The proof has specially polished planchets. And specially prepared dies. The Specimens usually may have somewhat polished planchets and just an early die state of the die.