Obviously with the weight of these things they must have been mounted by attaching something to the central bar. I have always been puzzled why they were designed to look just like a scaled up version of the 7x50 and 10x70 model.
The eye relief on the 10X70 is terrible even without wearing glasses with the rubber faceshield on. Once removed, though, there's a lot and it's easy to use with or without glasses.
It looks very much like the Ross Binoprism No. 5 7X50 because both are Porro II with the field lens cemented to the prism for max light transmission. When it was designed in the 1930's the British were not coating binoculars and a Porro II system with field lens cemented gave the best light transmission.
I'd like to see how the 10X80 was mounted. Seeger (grey book page 364) shows one with the original tripod adapter but notes the base plate is not original. Then there is this picture from a 1966 Charles Frank catalog, but I don't think the tripod it's on is correct for it. Note the Ross gunsight bino is mounted on the same tripod which probably isn't original to it either: http://www.flickr.com/photos/binocwpg/9587263574/