The final entry, dated August 15, 1977, sent a chill down Maria's spine:
: Sets a time for the AC to shut down (useful for sleeping). ECO / SLEEP ykr-f 006 manual
If your display shows HHH or LLL and the sensor is new, double-check terminal wiring. A common mistake is swapping the positive and negative leads of a thermocouple. CLASSIFIED DOCUMENT The Lost Manual The final entry,
EYES ONLY - LEVEL 3 CLEARANCE AND ABOVE