This is a hard-to-find telephone! The Bell System Model 2510 is a touch-tone desk phone produced by Western Electric for the Bell System.

The 2510F model included a CALL WAITING feature. It has a clear plastic knob to turn at top (see pic).

This phone was a transition from rotary dial to touch

tone. Bottom is dated as being made in Jan. 1974.

I believe the color was originally ivory, but it has faded to light beige in some areas. (Or could have been vice-versa.) Cords are beige. It has grey buttons & face.

Other than variations in color, it is in good condition. And a RARE find indeed!