Shortly prior to his retirement from the SER at the end of 1898 James Stirling produced his "B Class" 4-4-0 express engine which was not only a far more successful design than anything he had produced previously but also exhibited marked differences of appearance above the footplate when compared with his previous engines. There was a larger boiler, a squarer cab affording the crew better weather protection and a polished brass casting over the safety valve seating. The tender now had its springs under the footplate and was fitted with a larger, 3,000 gal, water tank.

Two engines, 454 and 459, were fitted with Holden's oil burning system in 1901. Although this conversion was a success it was deemed to be too expensive to be adopted generally and the equipment was removed in 1904.