7 Watt Duophonic Rackmount

(SOLD) READY TO GO!  US$499.  This Duophonic is a UBS and a Corona with a 7 watt EL84 output stage.   The WATTS control is actually P**** S****** but that term is trademarked.  Can anyone tell me what UBS stands for?  Price includes all tubes 12AX7's.  This is the FIRST of it's kind.  Own it today.  email me at phaezamp@gmail.com for shipping.  8 ohm and 4 ohm speaker connections.