Hi. First, double-check that model number. It should either be E-1, E-2, E-3, E-4, E-5, or E-6. I am not aware of any E-T but who knows??. Posting a photo would help.
In any case ... in perfect condition the organ is not worth any more than maybe a few hundred bucks. I tried selling my completely refurbished 1966 E-4 (solid state amp, 2-speed internal Leslie, colored tabs) for 500, then 300, then 100, and finally donated it to a local family. Maybe you will have better luck than I did.
If you care about keeping the organ intact, then don't give it away willy nilly ...or else surely someone will get a hold of it and rip out the Leslie parts and the tube amp (if it has a tube amp - not all of them did) , and maybe scavenge a few other parts, and throw the rest in the dump. I love these old Gulbransens and hate to see that happen to them. If you have to sell it very cheap or donate it, be sure that it is going to someone who will really appreciate it. Again that is only if you care what happens to it. If not, do whatever you wish with it. Good luck.