The important thing to recognize is that Zeiss was very capable and apparently willing to make one off or special models of their binoculars for those customers willing to pay the price. Steve Rohan has an interesting example of the 15x60 WW I era telescope modified, apparently by Zeiss, to take interchangeable telescope oculars.
Subject: Rubber Eyecups for Kern
From: michel bas <michel.bas@___ysurf.fr>
I recently bought a wonderfull 8x30 1978 KERN Swiss Army (with coated Lens) probably still with Zeiss glass
I am looking for new mint rubber eyecups
Is there a (Swiss reader of the "binocs-News" who might be able to supply me with these items
From the photos it seems me the green rubber wrapped Swiss binocs have the same euescups as my black 1978 one
michel bas /Paris
Subject: B&L 10x50 Mystery Binocs
From: "Jack Kelly" <binocs@___m>
I also have a 10x50 Prism Marine binocular described by John Anderson. It is also marked with a Navy acceptance engraving on the right front prism cover. Interestingly, I also have a 6x30 of the same design. It's marked "US Navy" on the left front cover and appears to be made up from parts. The back covers have the same 10x50 markings as the previous glass. (The 6x30 in my collection is marked 10x50 on the cover plate which makes me doubt a factory job.) The objective tubes from the 10x50 are interchangeable with the 30mm tubes and when interchanged both focus properly! Whether this was made up by some enterprising tech in one of the Navy service shops or a previous owner we will probably never know but Bill Beacom has seen similar models and was the one who pointed this out to me. I have attached a couple of jpegs of the two binoculars. You can see that the bodies, while similar, are not identical. Note the position of the hinge relative to the lug straps.
As for John's question on the early B&L binocular, the answer can be found in the B&L catalog from 1903 which lists three models, 5½, 8, and 10½ power, and provides the following explanation: “These Binoculars are constructed on the same principle as the Bausch & Lomb-Zeiss STEREO Binoculars, except that the objective lenses are no farther apart than the eyepieces are, hence the same degree of stereo-scopic relief is not obtained in the image. Next to STEREO, however, they are at least equal to the best to be found in the market and are put forward to meet the demand for a thoroughly reliable and high class prism binocular at a less price than that which the superiority of the STEREO commands.” The 8x B&L-Zeiss Stereo Prism binocular sold for $52.00 and the B&L 8x20 sold for $45.00 in 1903. Both were made in Rochester New York. The reason the B&L glasses were less expensive is that B&L was not required to pay Zeiss a royalty. The Zeiss patent was essentially based on objectives that were spaced further apart than the oculars.