Two letters were dropped in a letterbox in Amsterdam on Thursday. One with the stamp neatly top right and one with the stamp skewed and just to the left of the center of the envelope. Our hearts beat with anticipation when the postman walked up the garden path in Hilversum the next day. Does the stamp always have to be in the top right corner, or does an envelope also arrive if the stamp is stuck on at random?
“We prefer that the stamp is on the top right of the envelope. Our machines can recognize that best,” says Jack Lambregts. At PostNL, he is responsible for the software that controls the sorting machines, among other things.
Even before sorting by destination, it is checked whether the postage is in order. For most mail, this is done by the Sosma, the Shift Set Up Stamp Machine. The Sosma first pulls apart the mountain of envelopes. They go through the process one by one, in which the stamp is an important part. “A stamp contains a very small amount of phosphorus. If you shine a UV lamp on it, it briefly returns light. The machine recognizes where the stamp is, usually at the top right. The Sosma tilts the envelopes with the stamp downwards so that they are all at about the same height. This way they go neatly along the stamping head.”
Tilt help
The machine also sees ‘Postage paid’, black ‘bar codes’ and postage stamp codes (the 9 characters in a square that you can use as a private individual to frank a letter these days). To recognize reply numbers, which do not require a stamp, and to help with tilting, he also looks at the address block. “But if there is a stamp, it is leading. If you stick it to the back, that side will be put forward,” says Lambregts.
However, a wrongly pasted stamp is not immediately doomed. “The machine scans an area of the envelope, so a bit skewed is often just fine in the process.” If he really doesn’t see a stamp, he thinks the envelope is unstamped and then he goes to the hand stamping process. “We try to avoid that as much as possible. It is extra work, and therefore a lot more expensive to process,” says Lambregts.
The system is constantly powered
“The automatic recognition of addresses and postage is improved every few months,” says Johan Kapteyn, project manager at PostNL. “For example, we feed the system with more handwriting, he is learning. The fact that more and more of those stamp codes are being sold helps enormously in recognizing them better.”
Mail is in principle never lost. “It belongs to someone. If we can’t do anything with it, we keep it. Mail to Sinterklaas is sent to a Pietenhuis in Nuenen. Mail to God to the EO in Utrecht”, says Kapteyn.
At my request, Lambregts enters my zip code and house number into his system. Almost immediately two photos surface, of the two envelopes. “We did see that it had a stamp on it, but it wasn’t where the machine expected it to be with this envelope.” Yet that envelope also went through the automatic process, there is a tight stamp at the top right. The envelope with the correct stamp, strangely enough, has ended up in manual control and has a messier stamp. When the postman dropped both letters on the mat on Friday afternoon, it becomes clear why: the (empty) envelope with the correct stamp has been folded in half.
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