The circuit board inside it fella
It should have (if it is the ST-Z version) it will have a Z stamped on it
Or do the following:
'How to check if your HALO has Z code: While your HALO is running without paint in it, reach down with your fingers and stop the drive cone from spinning (you need to press down on it fairly hard to FULLY stall it so that it does not move at all). If you hold it down and the motor pulses three times and then the LED starts blinking red and green, you have Z code. If the HALO just keeps "humming" and does not stall out within 5 seconds, you do not have Z code.'
Dave