The Illinois State Police adopted the Model 39 in 1967 after a two year evaluation process. The agency’s first order of 500 guns were Model 39s, but the followup order of 600 guns was Model 39-2s. However, the State Police objected to the two different extractors found in the different models. Therefore, the original order of Model 39s were returned to the factory and retrofitted with a unique interim coil spring loaded extractor. Other police agencies also were given the option of having their guns fitted with the interim extractor. Many of these reworks will have the serial number stamped under the rear sight. Illinois State Police Model 39 handguns are easy to identify because they are stamped on the left side of the frame “ ILL. S. P.” followed by a property number. In 1972, the Illinois State Police placed a third order for 500 of the Smith & Wesson Model 59.