Thank you for pointing that out to me. I have just had a look at the advert again, yes it 6x9 but it comes with a 5x4 back. Being this is a old in years camera what would you expect they should go for. In the end it is only what the buyer is prepared to pay. It is displayed as very new, that is in use.
The Horseman fixed or focusing 4x5 adapter backs for the 6x9 technical cameras are OK for the occasional special situation, but IMO they are too clumsy and limited if your main purpose is to shoot 4x5. Much better to go for a 4x5 camera.
Graham, I use an Ebony SW45 which is great for wide angle photography but will only allow infinity focusing of lenses to 180 or a little longer if they're of the tele-photo design. I do use lenses up to 240 with the 'top hat' panel and extension tubes. An extension back is also available for using longer focal length lenses. But this of course all adds to the cost.
What I like about the SW it's of the non-folding design so will accept almost any lens attached when transporting. This design is compact and quick to set up, useful for those fleeting moments The bellows are also very supple and allows great flexibility with short focus lenses like the Super Angulon 47XL and the Apo Gradagon 35 (this lens will cover 6x12cm but not 4x5).