Turn it on, when it spins, move your finger in and out of the feed neck. If the hopper spins faster as you move past the eye sensor then it is a Z board, if the hopper feeds at the same speed when you are moving your finger in and out of the feed neck then its a Y board.
With paint, its easier. If the paint is fed fast, then when the paint runs out the loader slows down then its a Z board.
If its always the same speed, its a Y board