Now is the time to get dial gauges tested on pressure canners. Here are some reminders.
Most Extension offices have the Presto Gauge Testing Unit. This can test pressure gauges on the brands Presto, National, Maid of Honor, and Magic Seal.
This testing unit cannot test All American pressure gauges. Newer models of the All American canner have both regulator weights (weighted gauge) and the dial gauge. (See top picture.) The weight is more accurate than the gauge and customers should use the weight in order to determine if they are at the needed pressure. If the weight begins to rock at the desired pressure and the gauge is off by more than 2 psi the company recommends replacing the gauge. The gauge is now used as a reference to know when the unit is at 0 psi and can safely be removed.
Source: https://extension.psu.edu/pressure-canner-dial-gauge-testing