Hacking seconds

The mechanism the trade calls hacking seconds is documented even though the name is not. US patent 3,765,164, "Device to stop timepiece balance wheels", assigned to Timex Corporation and filed on 11 January 1973, covers a spring that "acts to bias a cock and also to selectively stop a balance wheel assembly": pulling the stem out to the hand-setting position engages the lever's stop portion with the balance and halts its oscillation, so the watch is not running while the hands are moved. A patent assigned to Casio Computer Co. Ltd, US 4,636,087, does the same job further along the train, an arm being "moved in the axial direction to engage with the top surface of gear 38 so as to stop its rotation" when the crown is drawn out.

No authority defines the term. US 3,765,164 notes that "This is sometimes called a hack feature", but neither patent uses the words "hacking" or "stop-seconds", and neither states the purpose usually given for the feature — starting the watch against a reference signal so that it agrees to the second. ISO/TC 114, the ISO committee whose scope covers horological "terminology; technical definitions", lists eight standards under its own direct responsibility, on jewels, control-position symbols, wrist-chronometers, battery life, chemical regulatory compliance, hard-material external parts and watch batteries. None concerns this function.

This Codex also looked for a military procurement specification requiring the function, which would be a defensible near-miss. The United States Department of Defense specification for general-purpose wrist watches, MIL-PRF-46374, is the obvious candidate, but a search of the Department of Defense's own ASSIST QuickSearch catalogue at quicksearch.dla.mil returned no record for that number in this session, and no official copy of the text was retrieved. Third-party mirrors exist and were not used, so nothing is quoted from it here.