The 1550 class was introduced in 1972. The class was built by Clyde Engineering/Comeng Rocklea and were the first locos in Qld to have the cut down nose.

The 1550 class used to work typically on general freight traffic around Queensland, along with passenger services. Some of the 1550 class were also used for Phosphate Hill phosphate mine.  All of the 1550 class have been rebuilt into the 2300 class.