It's one of the 150 HP models. The 180s end in 709, I believe. There are three different 150 part numbers. In a message dated 10/1/2004 2:20:17 PM Eastern Standard Time, RoboMan91324@aol.com writes: Hey gang, can anyone ID this number? 3831691 It is on the tag on the compressor but does not match the numbers I am familiar with. Thanks in advance, Doc