door This cover was sent aboard the motor vessel Diemerdijk (NASM/Holland-America Line) and processed on land in Balboa on 18 February 1952. As the ship sailed under the Dutch flag, it was franked with a Dutch 1951 semi-postal stamp: 6 cents + 4 cents brown from the series NVPH 573–577 (issued 12 November 1951). The surcharge was intended for child welfare; the postal value counted for 6 cents. These stamps were sold with surcharge until 31 December 1951 and remained valid for postage through 31 December of the following year.
Paquebot franking refers to mail posted at sea and received and cancelled by the postal authorities at the next port of call. According to standard UPU practice, the sender is allowed to use stamps from the country whose flag the ship flies. The postmark reflects the location and date of acceptance ashore; in this case, it is Balboa. When mail is handed over on land or within territorial waters, the postal rules and rates of the receiving country apply.
The notation “Posted at Sea” on the envelope serves a practical purpose. It indicates that the item was handed over aboard the ship and should be treated as paquebot mail. Such indications may appear as a typed note or a cachet. They help prevent confusion during sorting on land, especially when the postage does not match that of the destination country.
The envelope also bears the name “DIEMERDIJK”. A ship’s name on the cover — whether typed, stamped, or added as a cachet — creates a direct link between the envelope and the vessel. This is relevant for research and documentation: the name supports attribution to a specific ship and voyage and explains the presence of Dutch postage with a foreign port cancellation.
The ship Diemerdijk (also spelled Diemerdyk in English-language sources) was a post-war cargo vessel operated by the Holland-America Line, active in the early 1950s. It sailed on international routes, with regular transits through the Panama Canal. This makes a “Balboa C.Z.” postmark (“C.Z.” meaning Canal Zone) in February 1952 a logical part of the ship’s operations at the time.
The toponym Diemerdijk refers to the historic Diemerzeedijk near Diemen/Amsterdam. Since the Middle Ages, this dike protected the low-lying land from the Zuiderzee and formed part of a broader system of hydraulic works along the former sea coast. The Holland-America Line often named ships after Dutch waterworks and dikes; this name fits well within that tradition.
(The cover is lot 6407 in the Sheraton & Peel auction of 23 August 2025.)
