Convert from keel [coal] to pond [Dutch]

Unit Definition (keel [coal])
The keel is a traditional British unit of weight for coal. After considerable variation, the keel of coal was standardized in 1695 as 21.2 long tons, or 47 488 pounds (21.5402 metric tons). This is the approximate weight of coal carried at that time by barges on the river Tyne in northern England; the barges were also called keels, from the Dutch word kiel for such a ship.

Unit Definition (pond [Dutch])
The pond is the Dutch pound, historically about 494 grams (1.089 English pounds). This unit was also used in the former Dutch Indies (now Indonesia) and throughout Southeast Asia. In the Netherlands, the pond has been reinterpreted now as a metric unit equal to exactly 500 grams (1.1023 pounds), like the German pfund.