I cannot say anything about the origin of this handy slide rule with a
map of The Netherlands and a 'Cycle Import' ad. The name 'Cycle
Import, Tourism and Sport' says nothing to me.
The slide table determines the distance in kilometers between the places indicated.
I have seen other ones before, with exactly the same map and table, but with a different advertisement. For example a car driving school, and a car rental company.
A good dating is difficult
I found this card together with some early 1950s clippings. They were probably not been touched since. But this card could be older.
The map shown is not from the 1950s but from the 1930s:
on the map are shown only the 'Wieringermeer', drained completely in 1930, and the 'Afsluitdijk' (= Enclosure Dam), in operation in 1933.
I don't see any sign of the large 'Noordoostpolder' (= Northeast-polder) - fully drained in 1942 - nor of the Flevolands - work on the Flevolands had started in 1950 -.