If it works, it is well worth the (free) price. The E-100 is later than the B3 or C3, has a built-in amplifier and speakers in the cabinet (not a Leslie - if I remember right, a Leslie kit can be obtained to connect a Leslie.)
The E100 is a full size console with two 61-key manuals and a 25 note pedalboard. It does not have the reverse color lowest octave of keys like a B3 that select presets, the presets are selected by tabs above the manuals. There is a single set of drawbars for each manual.
The E100 motor is self-starting (does not need a "start" switch and a "run" switch. They were produced between 1965 and 1969, primarily for home use. I used to fix a bunch of them also in churches, sounded good through a two-channel Leslie. (they have a reverb circuit in the E100 that needs to be separately amplified from the main channel).
HTH,
Jim