The 6" Watts 770DCDA Double Check Detector Assembly was produced from 1993-1997. The body is a two cover, epoxy coated ductile iron construction. The check assemblies are stainless steel toggle linkage type. They use a vulcanized clapper plate. Check springs are contained when the cover is removed. Spring tension must be removed to repair the device. The device has replacable bronze seats, but a seat removal tool is required. The bypass device was a 3/4" Watts 007M1