Boss Pro GE-21
21-band graphic equalizer, each band covering half an octave and adjustable +/- 15dB. Made in the early 1990s.
Placed on the Pumpkins' official eBay account on 2011/09/29, ending on 2011/10/09 at $67.66. The accompanying text read:
Boss Pro GE-21 Graphic Equalizer. Used by Billy Corgan. The unit has been kept in a smoke-free studio environment. A 12 volt power supply is included. No other cables or manuals are included. A certificate of authenticity will be included. Unit is sold "as is".