Roger's rig for the Wall recording sessions at Britannia Row (1979) included Fender Bassman 50 amp with a matching 2x15" speaker cabinet (while for the Los Angeles sessions he used an early '60s Ampeg B18N blue Portaflex with 18" bass driver).
The Fender Bassman is a bass amplifier introduced by Fender in 1952. Although originally designed for bass guitar amplification, it became more known for usage as a normal electric guitar amplifier. When company began producing a reissue of the 1959 Bassman in 1990, that reissued '59 Bassman was re-categorized as a guitar amp rather than a bass guitar amp. (In 1993, David Gilmour used the 1959 reissue combo for the Astoria jam/recording sessions of The Division Bell album.)
The Bassman 50 model with silverface piggyback head that Roger Waters had during the Wall sessions in London, was manufactured by Fender between 1972 - 1977. It featured 50-watt RMS power with 110-watt peak music power, dual channels with separate control on each, "deep" switch in bass channel and "bright" switch in normal channel.
The latest version so far is the '59 Bassman LTD guitar combo. The LTD version has a lacquered tweed covering and 4x10" Jensen speakers instead of the Eminence speakers used in the earlier '59 Bassman reissue series. In 2012, Fender introduced the Bassman PRO series of heads and cabinets, which are primarily targeted at bass players.
Source: Wikipedia, Fender