I mentioned this on FB and this is how I was taught to RO.
-last shot, shooter is finished-
RO: "ULSCH"
RO: (LOUDLY) "TIME!!! SIXTY SEVEN FOURTY TWO!!!"
RO: (shows timer to shooter as score keeper recites time they are entering)
ScoreKeeper: (LOUDLY) "TIME, SIX SEVEN FOUR TWO!!"
RO: "Scoring is complete!!! RESET!"
This has the double checks in place and is loud so the other competitors can hear the time called, the verification called and the shooter verifies against the clock