Nylon-stringed acoustic guitar by C.F. Martin [wiki], used to record "To Sheila". It went up under the Pumpkins' official eBay account in April 2010 (reserve not met at final bid of $5,100), and again in June 2011, with the auction ending on July 3 at the same price as before- $5,100 (reserve met this time). The auction listing included the following note:

1947 C.F. Martin 00-28G Acoustic Guitar. This guitar was used to record "To Sheila" off of the Smashing Pumpkins 1998 Adore album.

 Serial number: 99070. This guitar comes with a hardshell case. Note: Due to the history of the guitar, there are some minor nicks and scratches on the guitar. This auction also includes a copy of the Smashing Pumpkins 1998 Adore album on vinyl signed by Billy Corgan. A certificate of authenticity personally signed by Billy Corgan is also included.

The winning bidder has sent us a few updates: the actual serial number is 99075 (the wood fibers at the top of the stamping were crushed, making the 5 look like a 0 at first glance), and that while the 3 higher-pitched strings are nylon (G-B-E), the lower 3 (E-A-D) are steel (the steel strings' squeaking can be heard during some chord changes). The guitar was also used to record other songs besides To Sheila.