Isle of Man Ports:
18p Douglas, she is the largest harbour of the islands, and the ferries terminal is there. The ferry visible is the KING ORRY V. viewtopic.php?f=2&t=5992&p=5988&hilit=KING+ORRY+V#p5988
23p Castletown, situated in the south of the Isle of Man, the harbour is dominated by an ancient castle. In the harbour alongside are some pleasure craft visible.
37p Port St Mary, Port St Mary is the principal harbour in the South of the island. It handles coastal vessels, supports a buoyant fishing industry. The stamp shows fishing vessels, cabin cruisers and yachts.
40p Ramsey is the second busiest harbour on the island, dealing with mixed cargo, fishing and pleasure craft. The red hulled cargo vessel on the left of the stamp is the GLENFYNE,
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Source: Isle of Man Post Office information letter No 63.
Isle of Man 1992 18/40p sg 527/30, scott 519/22 and MSsg 531, scott 523a/523b. For the MS see also: viewtopic.php?f=2&t=5992&p=5988&hilit=KING+ORRY+V#p5988