At over 35 years of service, this Safe-T-Lawn ball-drive rotor head was a leaker, but unlike a PGP, a leaker that can be fixed. Held together by stainless steel screws, disassembly is routine. Note the restriction where the water enters the head, which acts as a sort of surge protector. Here's the STL 'keyhole' nozzle, to which today's Rain Curtain nozzles owe their existence. Because the head had become covered in dirt and mulch, it was only necessary to clean out any dirt and grit from inside the head, and reinstall it at the proper grade. Back in business.