256.617.  Drilling rigs, how marked — rig permits. — All permitted water well drillers shall see that all rigs used by them or their employees in the water well drilling are marked with legible identification numbers at all times.  The identification number to be used on the rigs shall be the permit license number which appears on the driller's permit.  The rules and regulations adopted by the division shall set out in detail the specific method and manner for marking the rigs.  A separate permit shall be obtained for each rig operated by a permitted water well driller during permit year.