Originally developed by ATEA this model was adopted as a standard telephone by RTT in the late 70s and produced by both ATEA and BTMC.
This is the deluxe version, covered in leather. The only thing that shows its maker is the letter B on the bottom. ATEA built versions had the letter A at the bottom.
The inside is totally devoid of any markings or writing.
An ancester of the Unifoon in the Netherlands, which was push button only.