I have an EH4800 Phase Shifter. Its in good working order. Judging from the Serial Number on the pot (1377823) and reading other threads on this board, I believe its from 1978. Im interested in selling it, but I cant come up with a price since there is such a wide variety of prices on Ebay, Reverb.com, etc…Can anyone give me some advice on setting a price or an appraisal. Thanks