Richard Fisher, KI6SN, had a post back in August 2009 that talked about an interesting transceiver that was in use by the military in the 1960s and 1970s: the AN/PRC-64. The radio is crystal controlled, limited to four channels between 2.2 to 6.0 MHz, has a max output of 5W for CW and 1W for AM PHONE. Its distinguishing factor is the rigs small form factor: 9.8 x 5.1 x 4.7 in.
What really makes this a spy rig is its ability to be paired with another device: the AN/GRA-71. The AN/GRA-71 is a burst encoder. The encoder allows the transmission of CW messages of speeds up to 300 wpm… some serious QRQ.
A government evaluation report on the radio concluded, based on tests conducted in Vietnam supporting Special Forces teams, that the radio had an effective range while operating in CW mode of between 40 and 300 miles. I imagine with both the power output and frequency range (and assuming the use of a field expedient wire antenna) the radios were not normally used for long haul communications… probably more like a range of not more than 75 miles.