If I had all the time in the world, I would start a thematic collection of windmills. I find them fascinating and an object which looks so great on stamps. But I haven't, so I just collect bits and drops. There's beautiful Portuguese stamps with windmills on, which I will try and find for you soon, but today I'm showing you part of a Dutch set with windmills on, from 1963. Stunning!
The 4c shows a tower mill. These are usually found within built-up areas. They therefore have to be high enough to still catch wind. Halfway, there is a gallery or balcony (where the railings are) from where the miller can operate the wings.
The 8c shows a polder draining mill. These mills were used to drain water from the polders.
The post-mill shown on the 12c is the oldest wooden type of windmill in the Low Countries. The top bit rests on a post and can turn to face the wind.