Nice coin, assayer is "F" (left side of big "Y" in gothic script) corresponding to Francisco Rodriguez (assayer 1542-1578). Santo Domingo (mintmark S P, you must turn 180º) mint was established in 1536 and it seems that first coins were issued in 1542. Then yours could be dated ca. 1542 to 1564 (most scholars opinion), last of them into Philip II reign (he ordered ca. 1570 that all coins were minted with his name).
v.