What makes this Utrecht 1684 ducat a special coin is the countermark “B”, for Batavia.
Batavia (Jakarta today) was a primary city of the Dutch East India Company, known as the VOC from its Dutch name. Because the Netherlands gold ducats were trade coins, invented for use in international trade, a large number of them were transferred to Batavia on ships. With the fleet returning to Europe with precious spices, pepper, silk, etc.
As for the coin, the value of the Netherlands gold ducats in the VOC was higher than their value in the Netherlands. So to protect themselves from coins being smuggled onto ships traveling to Batavia by the crew, in August 1686 the VOC ordered that the 20,000 Dutch gold ducats deposited in the VOC Treasury be marked with the “B” mark for Batavia. In 1700 another 49,495 ducats were marked with the “B” countermark. However because the countermarked ducats were easily falsified they did not succeed as the VOC expected.
Gold ducats with the “B” countermark are very rare and sold for high prices. The example sold recently in a CNG auction for $14,520 was sold previously in the Spink-Taisei auction 19, on February 23, 1995 (R.J. Ford Collection) for $8,970.