Radiotelefoondienst

In October 1936, the PTT needed to inform people how to use radio-telephone, a two-way, long-distance voice communication system using shortwave radio to connect remote locations in the Netherlands and Dutch East Indies—and, boy, does this one really spell it out. Designed by N.P. de Koo and broken into easily manageable chunks, it leaves room at the back for adding phone numbers and notes. Breaker breaker. Over and out!