Pre EEC/FADEC, you would obtain a reference for max thrust from tables as part of TO data calculation.
This would usually reference a target N1, or a target EPR depending on engine/aircraft/customer preference, but would vary depending on ambient conditions. There was no single N1 figure that represented max thrust.
These days, the a PFM does the calculations and puts a nice little red arc on the appropriate gauge, and this USUALLY represents fire-wall thrust- levers.