Possible Clues:

• Supervisory body recalling both pistol and round
• Controller
• Controlling device
• Controller of number of vehicles you subsequently overheard
• Soldier sent round to part of the watch
• Controller turned over a weapon to resistance leader
• Mechanism for controlling fluid flow, pressure, temperature etc.
• Monitor to be included at frequent intervals
• Got a ruler replaced as a means of keeping good order
• Scuba device