GTE, but what is it?

[countryman]

I don't think I've seen it before.

https://www.ebay.de/itm/115114039945

[stub]

countryman,
                Here's all I have on this phone. The Linear UDK telephone provided the speed and convenience of push buttons by the use of special electronic circuits it signals the telephone central office with standard pulses like a rotary dial. Sorry about pics , that's the best this old camera will do. Hope this helps. stub

[LarryInMichigan]

I remember seeing those for sale all over the USA somewhere around 1980. 

Larry

[compubit]

There was also a Touch Tone version with the * and # on the far left end, IIRC...

Jim

[paul-f]

There was also a Touch Tone version with the * and # on the far left end, IIRC...

... and a wall  model.