It is the speaker part of a 3A or 3B speakerphone set. It is not a Spokesman® or the ITT clone, the Orator®.
The Spokesman (model 107A or B) has an amplifier inside and a 4- or 6-conductor cord. It has a volume control on the front faceplate.
ITT also made a two-way talk-back system that used a similar-looking item, the Call Announcer®. It used the same form factor but had an additional switch on the roof, and an LED busy lamp.
Call Announcer It homed in on a special dial-selective intercom unit in the 76A KSU.
The faceplate is matte finish. A CORD (not cable) in -51 can be located easily. You can use one that has more than 2 conductors, of course. Now you need to find the 666 transmitter and the 55B control unit. Good Luck!
