Tortola was settled by the dutch in the mid 1600's. Before official settlement it was used by pirates such as Blackbeard and Captain Kidd as a haven. The English took control of the island in 1666 and established a plantation colony. These pieces were cut and counter stamped from captured Spanish coinage between 1805 and 1824 for general use around the island. The coin was denominated as 4 shillings 1.5 pence.
I understand that the Tortola counterstamped coins are also quite scarce, and occasionally counterfeited. It's good to have a solid authentication on the piece.
I actually picked up a small collection of Caribbean counterstamped pieces and other coinage yesterday. I'll post new threads as I get time.