If you have an oscilisope you could hook up a chanel to it and rotate the motor at a known speed and get the pulse rate that way.
If you dont then hooking up to Mach and zero the encoder DRO and rotate the motor 1 turn and you should get a reading in the DRO. Never tried that so I am unsure how Mach is expecting things but would think best to set the Count unit to 1 and see, if the reading is exceptionally low then you maybe multiply that by 4.
The encoder may however not be an incremental one, are there any markings on it?
Hood