I picked up a similar 648A a few years ago that I have since sold but did take some photos.
Here's one of the back. I also
https://flic.kr/p/6okuzE
I also have an Emerson 637A with back but it is in a wooden cabinet and a model 614 in bakelite.
Here are photos of my 637A
https://www.flickr.com/photos/700398...57672714173057
Are you sure about your model # ? I'm pretty sure you actually have a model 614D