5531 is a 1959 Chevrolet tanker manufactured by Simms Fire Equipment Co. in San Antonio, Texas. It has a 283 cubic inch V8 gasoline engine, 3-speed manual transmission, and a split rear end. The GVWR is 19,500 pounds with a 1,000 gallon tank capacity. The pump capacity is unknown, but it is a positive displacement gear pump with two suction inlets, one discharge, two pre-connects, and a dump valve at the rear of the truck. It was sold to a private owner in August of 2011 and he intended to keep using it as a tanker truck to haul water across his ranch.