Vintage - The Phone Silencer - Zoom Telephonics Inc

Description

This things is old. The instructions show how this device can be added to your phone and the phone pictured in the example is a rotary dial phone. That's old.
Looks like this device is meant to be a silencing switch for your phone. Your old phone.
And I think it's ironic that the company that made it is called Zoom Telephonics Inc.
Makes for a cool display, conversation piece.