A.J. De Koning’s slides are one of the special collections brought together by the Dutch Mill Association over the course of time. During the years he was working for the association, first as a technical advisor, later as the managing director and also for many years after he had retired, De Koning took photographs of the Dutch mills he visited. From the early 1960s through to the mid-1990s, he photographed the national symbol of the Netherlands from various angles.

Restauraties, reparaties, openingen en vele andere gebeurtenissen op en rond de molen zijn vastgelegd op de gevoelige plaat. Ook werden (delen van) molenruïnes gefotografeerd. Omdat De Koning een beperkt aantal filmrolletjes had, nam hij de tijd om zijn foto's te maken. Doordat hij zo nadrukkelijk op zoek ging naar de mooiste hoek, de beste lichtval en het meest karakteristieke beeld van de molen, ontstonden unieke opnamen. Gemiddeld werden twee foto's per molen gemaakt die later werden ontwikkeld tot dia. De complete collectie is digitaal beschikbaar in het Geheugen en telt ruim 9.500 afbeeldingen.

The images of the mills are ordered according to their type, location (province) and the day or month they were photographed. Thanks to this classification, viewers notice immediately that there are many types of mills. Mills in each region have their own more-or-less characteristic shape and function. Many watermills are located on the edge of the National Park Veluwezoom in the province of Gelderland and on the domains of the Het Limburgs Landschap Foundation in the province of Limburg, while the Provinces of Noord-Holland and Zuid-Holland feature a large number of drainage mills. A special type of mill is the tjaske, that is almost only to be found in the Province of Friesland. The collection has links to descriptions of mills, maps and images from other mill collections and may be viewed at allemolens.nl.