Netherlands Railway Stamps don't get much attention, but they have a lot to offer.
Early examples largely shared this general design:
The first ones were inscribed Nederlandsche Staatsspoorwegen
in the bottom tablet. This one is inscribed Nederlandsche Spoorwegen
, and I believe it is from the 1924 series. Other inscriptions, for other Dutch railways, also exist.
These were printed by Joh. Enschedé & Zonen, Haarlem, and this is the most-common value, by far. Almost all of the values are found in this color, and in red. This color was sold at railway stations, and the red versions were sold through other channels. One site says that usages for the red versions included private couriers; the site linked below says "other distribution and transport centres."
Hans Vink has a great site for these. Some old link sites have a broken link, so here is a current one:http://web.inter.nl.net/hcc/H.Vink/rwletstamps.htm
Any additional information or examples would be great.