The Dossier Dead Drop
(Downloads)
Foreign agents would arrange to deposit and retrieve payments or information at secret locations called dead drops, a form of asynchronous contact so that the target country's counter-espionage forces would never see the two spies interact directly.

RP=Realpolitik-style, provides the familiar look.
DX=Deluxe, evokes vintage Diplomacy's physical map & wooden units with all the heraldic color of fluttering war banners.
Insert both DX & RP versions into your  Realpolitik Variant_Files folder.