'Mercury' airmail stamps

Because I obtained a payment receipt bearing two 1-guilder airmail stamps and a 75-cent airmail stamp, I went looking for more information about the stamps featuring an image of 'Mercury'. The payment receipt was for an authorization to collect mail addressed to PO Box 235 in The Hague. This authorization was only valid if the fee of ƒ 3,75 was paid in stamps. You wouldn't immediately think of sticking on airmail stamps in that situation! Let's first see what has been written about the airmail stamps featuring the image of Mercury. In PTT Service Order No. 473 of June 26, 1929, the following was reported: 1. Airmail stamps of ƒ 1,50, ƒ 4,50, and ƒ 7,50 have been issued, serving exclusively to account for the air duty due for the direct transfer of items by means of aircraft from the Netherlands to the Dutch East Indies, Suriname, and Curaçao, and to other countries for which mail was permitted to be transported by these aircraft. 2. The stamps bear a representation relating to aviation. By way of explanation, the PTT Head Office stated that during the last mail flights to the Indies, the need for stamps of higher value became apparent, because on several occasions, a larger number of 75-cent stamps than desirable had to be used to satisfy the air duty due. The three stamps were designed by the Rotterdam artist Jac. Jongert, who chose Mercury as the image of the protector of trade and traffic. Beneath the wings of the hat, he added a Mercury staff against a background of a blossoming earth, which symbolized prosperity. The three stamps were made available from July 16, 1929. The print runs (the number of printed sheets of 100) were also announced at that time: 3.500 sheets of ƒ 1,50, 2.500 sheets of ƒ 4,50, and 2.500 sheets of ƒ 7,50. Mr. A. van der Willigen, a well-known philatelist of the time, reported that ƒ 4.000 worth of these stamps had been sold at the special counter for collectors at the post office in The Hague alone during the first week of sales. So, purely for collecting purposes! The stamps were, in the opinion of many collectors, beautifully executed, but the centering was often very poor. This was due to the use of line perforations. Had this expensive series really been necessary? As early as October 1929, it was announced that the airmail duty for mail items to the Dutch East Indies no longer needed to be paid with the special airmail stamps. Back to the authorization card for the post box. In February 1930, the following was included in a Service Order of the PTT: Recently, requests have frequently been received from box right holders to account for the due box duty by means of airmail stamps. Such requests may not be complied with. In March 1930, it was further added that the payment of airmail duties no longer needed to be made with airmail stamps, but could also be done with normal postage stamps. However, it remained prohibited to use the airmail stamps as ordinary postage stamps. But then the policy changed. Had too many stamps in the high denominations for airmail duties been produced after all? By Royal Decree of March 20, 1931, it was determined that, effective April 29, 1931, the airmail stamps of 40 cents, 75 cents, ƒ 1,50, ƒ 4,50, and ƒ 7,50 could be used for the discharge of all prepaid charges and duties. This therefore meant that the stamps could no longer be used exclusively for airmail correspondence, but were also valid for franking all correspondence, both domestic and international. The holder of PO Box 235 was therefore happy to make use of this possibility. But were the large stocks of these stamps quickly cleared away? Far from it! The sales figures prove this. Of the 350.000 stamps of ƒ 1,50, 329.100 were sold, so that wasn't too bad. Only 20.900 stamps remained. Of the 250.000 stamps of ƒ 4,50, 189.900 were sold, leaving 60.100 stamps remaining, and of the 250.000 stamps of ƒ 7,50, 195.400 changed hands. Of those, 54.600 stamps remained.   I still find collecting PO box authorizations, or PO box cards, a fun challenge. Like the PO box card valid for six months in 1971, affixed with a 10 guilder stamp. Just try finding one!