I worked for Automation Industries, the owners of the Sperry Rail Service, from February 1977 until December 1979. In that time I managed to work on all three rail cars in Australia at the time. The history of the rail cars in Australia, as far as I know it, is in "The Rail Cars" page.

The Sperry Rail Service was founded by Dr. Elmer Sperry (who is said to have patented more inventions than Thomas Edison) an electrical engineer whose name, at one time, featured in a lot of Corporate identities. In the 1920s he was asked to develop a means of identifying flaws in rails before they broke, a common cause of derailments at the time. He developed an electro-induction testing method that proved effective in locating internal cracks and flaws in rails. His original intention was to license the technology to individual railways who could build and operate their own testing vehicles. However, the railways weren't interested in that idea so he set up the Sperry Rail Service, had test cars built and hired out their services to the railways. Sperry was basically a inventor and developer so he soon sold the rail service. It passed through a number of owners before being acquired by Automation Industries. I noticed that in the early 1980s ownership had again passed on this time Penn Central Railways. Today it is owned by the Rookwood Corporation.

If you can find a copy, the January 1979 edition of Railfan Magazine (USA) has an article on the Sperry Rail Service including a listing of all the rail cars up to that time. The Links page has links to both the Sperry Rail Service and several unofficial pages on the subject.