My tractor has a 3 speed pto. 540, 750 and 1,000 rpm. All at 2,200 rpm.
I put a tach on the shaft to figure out the engine speed to get 540 out of all 3 speeds.
My bolens/iseki tx2140 runs just under 540 PTO RPMs at 2600 engine rpms in PTO 1. It has a small red dot on the tach that I presume means PTO speed. I've been able to also get 540 PTO RPMs at 2000 engine rpms in PTO 2.