Created by Don A. Sillers, founder of Peerless Manufacturing, and Alexander Clarke, this early Type M gas odorizer—Serial No. 2105—served from 1942 to 1992. It injected a precise amount of pungent liquid into the gas flow. The patent was filed June 18, 1939, and granted (2,240,808) on May 6, 1941. The Type M odorizer established itself as a dependable, long-lasting safety device. This particular unit operated 25 years without maintenance.

The meter-type gas odorizer was developed a few months after 294 school children and adults died in a natural gas explosion in a New London, Texas, school. The Texas legislature responded by requiring natural gas to be odorized so that leaks would be apparent. By the end of World War II, natural gas had established a reputation as a safe fuel largely because of odorizers.

Initial designs of gas odorizers used the evaporation principal for introducing odors into a gas stream and most were marginally ineffective due to fluctuating flow and pressure. The Peerless odorizer used a residence-type iron case gas meter, modified to drive a dipper-type pump. The complete assembly was enclosed within a pressure vessel at line operating pressure. Odorant was introduced in a measured amount, remaining proportional over a wide range of flow rates and pressure changes up to 50 percent.