6-string bass with a 30" scale (about halfway between a standard bass & guitar).
Placed on the Pumpkins' official eBay account on 2011/11/18. The accompanying text read:
Jerry Jones JJ Original Longhorn Bass6 6-String Bass Guitar. Serial #438. Serial number is hand lettered in black ink at lower back of headstock. This guitar was manufactured between mid 1988 to mid 1990. This guitar comes from the collection of Billy Corgan. A hardshell case and a certificate of authenticity personally signed by Billy Corgan is included.