Strange. I'm just asking the Lisp system:

    CL-USER 1 > (class-of *standard-output*)
    #<STANDARD-CLASS EDITOR::RUBBER-STREAM 40E035A2E3>

Oh, the class of the value of

    *standard-output*

is EDITOR:RUBBER-STREAM... From there I can find the source, find the applicable methods, the slots, the super classes...