Developed jointly by SEL (Standard Elektric Lorenz) and BTMC (Bell Telephone Manufacturing Company) in the late 50 it broke with a lot of traditions and was far ahead of its time. A simple and compact telephone, with new electronics and made of new and modern materials. It was one of the first telephones in Europe to make use of a thermoplastic housing and was one of the first telephones that was in a standard grey. Many similar grey telephone designs would follow for decades to come.
Also made in a wall version, it has a white earthing button. The ringer has concentric bells to save space and the volume was adjustable with a button in the base plate. It was supplied for private installations and exported all over the world and produced in several different locations.
A similar advanced and innovative model was the Siemens & Halske Fg Tist 282, which was released in about the same period.
In the 60s most national telephone companies in Europe commissioned their own grey plastic standard telephone. Many were derived directly from the Assistant, like Heraldo from Spain and the FeTAp 61 from Germany. As the Heraldo and FeTAp 61 used the same body shell, it is hard to tell the difference from the outside. The electronics inside are different though, as is the underside. Furthermore the Assistant lacks the grip at the rear.