Mark,
Are you referring to the outlet on the interior of the truck? If so, a breakdown is in the ORD 9 for the 5 ton wrecker - maybe in the -20 or -30 as well (I tend to use 1950s era books rather than the later ones.)
Or are you referring to the slave receptacle that is on the outside of the truck? (or the plug that inserts into it?)
Just saw your second post - so I presume we are discussing the slaving apparatus. I've had the plug apart on one of mine - but I don't remember the details. I should be home later today and hence able to look at it.
Best,
David