Reeves Custom Jimmy amp head
A re-creation of Jimmy Page's (Led Zeppelin) HIWATT amp used ~1969-71. The amp has a foot switch that controls a volume cut adjustable on the front, allowing it to be fed a "more aggressive preamp tone" (as Billy seems to like), then switched to a cleaner tone- similar to a 2-channel amp, but not.
Used w/ the Bat Strat to record Chimera during the Oceania sessions, as tweeted by Billy on 2011/07/12: "Can't say enough good stuff about Reeves amps."
Mentioned again in an 'Oceania track-by-track' interview in 2012: "With a song like [Quasar], I know we were using a combination of a Marshall Super Tremolo amp with four rhythm guitars, and the other guitars went through a Reeves Custom Jimmy head, which is the re-creation of Jimmy Page's Led Zeppelin I amp. It's incredible."