WAGR Os class

The WAGR Os class were a total of 5 experimental steam locomotives operated by the Western Australian Government Railways (WAGR) from 1915 to 1937.

The Os class were the result of superheated boilers being fitted to Nos. 81 (later 210), 94, 99, 212, and No. 220 with Sir Vincent Raven's patent bypass valve also fitted. By 1937 all had been converted back to standard O class locos, though Os boilers were later exchanged with N class ones.