It can further be narrowed down as being between 1568 and early 1571. In that year the pillar and waves changed to the cross. It is almost certainly assayer R (Rincoln), because there are no known examples of a 2 reale denomination with assayer X (Xines) who replaced Rincoln in 1571. Sewal Menzel's book "Cobs, Pieces of Eight and Treasure Coins" refers to your coin as a sub-type Ic (because of the "VSV" being between the pillars).
Stan