Ask Square-D? There are still some old-timers around that may have an old catalog or two. Other than that, it's not something that anyone else would worry about.
Generally ammeters always use 5A input unless they are under 10A. The scale is based upon what you will read from the CT ratio feeding it. The rule of thumb on CT ratios is to have the ratio match the top end of the ammeter scale range, but make the range twice what you expect to read so that the needle is near the center when displaying normal conditions. For insance, if it is a 100A meter scale, it would have used 100:5 ratio CTs, but would have been used for a system consuming between 40 and 60A normally. If you were going to consume 80A normally, you would use a 150:5 CT and a 150A scale plate on the meter. Not much has changed about that in the 30 years I have been messing with this stuff.
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
