Per Queensland Railway's classification system they were designated the PB15 class engine, P representing they were a passenger locomotive, the B that they had three driving axles and the 15 the cylinder diameter in inches.

By 1912, a total of 202 engines had been built by Walkers (122), Evans, Anderson, Phelan & Co (70), Kitson & Co (20) and Toowoomba Foundry (20).

In March 1922 however, due to poor performance it was converted back to its original tender form.

[2][4] In 1924 one example of the engine was built by North Ipswich Railway Workshops for the Aramac Shire Tramway.

[2][4] In 1932, a number of PB15 class locomotives attached to Ipswich depot were fitted with a second sandbox for rear sanding to assist with shunting work on the colliery branches.