There has been one difinitive book written about Zenith Trans-Oceanics and it is: "The Zenith Trans-Oceanic" written by John H. Bryant, AIA and Harold N. Cones, Ph.D.  It covers all the Zenith Trans-Oceanic's made but also has a wonderful section on the Bomber 7G605.  This is a Schiffer Book for Collectors and can be bought on Ebay, Amazon etc.  Easy to find.   The Bomber is the first Trans-Oceanic Shortwave Radio ever made and was only made in 1940 to 1941 when Zenith stoped production for the war effort.  This is the rarest of all the TO's.  Only about 35,000 ever made and I would guess only about 5,000 still survive at this time (2006)  They were expensive but as time with on they lost there value, as they would break and them be stored away with both batteries still in the radio.  After a few years the battery would corrode the inside of the radio and ruin it.  Thus it would be throw away or contiune to deteriate.  The radio's that survived were intentionally stored in a safe place and this was not many.  Some also were lost in the war effort and were left overseas by returning solders.  Gifts to the locals.  This radio is the hardest of the TO's to restore.  It has many difficult parts to replace and some must be resored by hand.  Also the front of the radio will need intesive work to bring it back to original.  If you wish to email me I would be happy to supply you with more details.  Thanks Rick Conn