I'm not the right guy to answer that one. I found the site for more info on an early '50's GE Twin Ventilator I'm restoring.
If I had to pick a number out of the air I'd guess $20-$40 but let the fan gurus answer that one for you. Just like GJ'ers, there are always folks asking what to pay for something/what something is worth. Vintage fan collecting is not a high-dollar hobby from what I can tell.