The 2" Watts 007 double check assembly began production in 1989. The original 007 was replaced with the 007M1 in 1991. The "M" stands for modification. The 2" 007 went through one modifications for a total of two different models (007, 007M1). Repair parts do not interchange between originals and "Modification" models so be sure of your model before ordering repair parts. The 007 is an inline check design with a single access cover. The body is of bronze construction. Fully testable.