The following sounds like a description from the world-wide game “geocaching” rather than a quotation from the Communist State Security archive materials: “An inland drop box is usually made in the roots of trees, bases of remote sacral monuments, benches in parks, road verge posts and electricity poles, at waste dumps, cemeteries, walls, sewers etc. Very often secret messages are placed shallow in the ground in metal boxes or in bottles with impermeable plugs.”
The file located in the archival collection Kabinet státobezpečnostních materialů/ Various Security Materials (Code 323) under Inv. No. 323-7-2, comprises findings about so called dead drops (also known as dead letter boxes). This peculiar document was written probably in 1951 and reflects the efforts of the Communist State Security to reconstruct a system of so these boxes that should have served as kind of info points for spies where various pieces of information were gathered on the training of spies abroad and building their contacts with the people of Czechoslovakia.
These devices served mainly for passing messages between the members of home resistance and foreign secret agents, and the State Security started to uncover them as early as at the end of 1948. Most of these boxes were discovered in Plzeň, České Budějovice and Karlovy Vary regions, and exceptionally also in Prague.
The dead drops were divided by the State Security officers in two main groups: live, i.e. operated by two living persons who meet to exchange items or information, and dead, which were divided up in inland dead drops and border dead drops.
Usually encrypted messages or money used to be placed into the dead letter boxes. The State Security tried to eliminate these “drop boxes” in a deliberate and systematic way, as we can see from one of these records: “Some State Security officers laid in hiding near the roads that led to the dead drop. They were covered by camouflage tarpaulin and earth and communicated via a string. They had to be patient and remain in their positions for the whole night. They managed to pursue a man who collected the messages from the box and they still keep him under surveillance in his everyday life so all his contacts can be uncovered.”