Joe, nice find!! The cord on that buttset is what is known as a CO [Central Office] cord. The plug/jack assembly near the bottom of the buttset allowed switching the "business end" of the cord for different uses: there were plugs/clips/what-have-you that would connect directly to a main distribution frame and/or CO protector block [usually on the MDF], there were cords for ground-start line testing, there were even cords with the 310 plug we were talking about earlier.
Surf on over to
Aines to see all the different kinds of cords. They also have the "bed-of-nails" clips that a typical field buttset would have, if you want to convert your set.
I'll leave the color question to someone else, I too would like to hear the "inside dope" on that.
Jim
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Speaking from a secure undisclosed location.
