White Princess 2712b and 759A Interphone Antique Mall Find #1

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I started a thread on four phones and returned to the antique mall for this one:
http://www.classicrotaryphones.com/forum/index.php?topic=27351

I wound up getting it for $22 after pointing out the defects in the plastics. I think the desi card strip chips could be left alone,  filled in with a sliver from the inner shell and sanded, or replaced with a new case altogether.  Amazingly, the missing thread on the handset still holds a cap.  I took a mini screwdriver with me but couldn't open the case. Based on the wired interphone I hoped that I might find a transmitter in the base and when I got it home I did. The station cord is covered in beige latex paint but white. I cannot see the restraint marks under the internals but the handset cord is 1970. Everything else is 1970. I suspect the modular jack is an add-on and the cover for the interphone wall unit is nowhere to be found.