During the 1950s a relatively straightforward concealment device was developed and used by covert operatives on both the sides of the East and the West. A hollow nickel case, in the shape of a coin was used to transport secret messages, film and even poison undetected. Not well dressed spy would be properly equipped with dual purpose cash in his pocket!
The Office of Technical Readiness used people with clothing knowledge to dress spies in unremarkable clothes that would allow them to blend in and disappear into a crowd. The clothing itself could be equipped with covert recording equipment behind a broach or badge, a compass in the buttons and most well know, garotte wire in shoe laces.