Map or book?

 The folding system used by these maps is protected by patent - up to 1978, the date of this example (Cologne), over 47 million had been sold. Maps of 45 other German cities were available then; more, now, probably...

The folding arrangement allows the map to be handled like a book. You simply open it, and fold down the flaps, rather than having to open the whole map.

The company, Falk, has been making maps for some 60 years and, as you might imagine, is now heavily into satnav.