Between 1910 and 1912, A Pengelly & Co of Adelaide assembled 50 bogie closed combination trams for the Municipal Tramways Trust (MTT) from knock-down kits manufactured by the JG Brill Company of Philadelphia.
[1][2][3][4] Numbered 121-170, they were built to provide increased passenger carrying capacity for the planned expansion of Adelaide's electric tramway network into the outer suburbs.
[2][3][4] All were delivered with 22E bogies, the sets under 121-125 being manufactured by JG Brill Company, the remainder by Brush Electrical Machines.
[5][6] Meanwhile, in 1912 Duncan & Fraser (Adelaide) had built four almost identical trams (there were only slight differences in detail between the trams of the two manufacturers, such as the Duncan & Fraser cars having concave rocker panels rather than convex); for the Prahran & Malvern Tramways Trust in Melbourne, and were allocated numbers 21 to 24.
[2][3][4][7] All passed to the Melbourne & Metropolitan Tramways Board (MMTB) on 2 February 1920 when it took over the HTT, being renumbered 127 to 130 and designated the O-class.