Iowa Code § 215.19: Automatic recorders on scales.

Except for scales used by packers slaughtering fewer than one hundred twenty head of livestock per day, all scales with a capacity over five hundred pounds, which are used for commercial purposes in this state, and installed after January 1, 1981, shall be equipped with a type-registering weigh beam, a dial with a mechanical ticket printer, an automatic weight recorder, or some similar device which shall be used for printing or stamping the weight values on scale tickets. A scale equipped with a malfunctioning automatic weight recorder may be used for not more than seven days if the device is unable to print or stamp the ticket so long as a repair to the automatic recorder is immediately initiated and the user dates, signs, and accurately handwrites the required information on the ticket until the device is operational.