You are right: if this kind of marking is not widely known by collectors, such binoculars could not be a mass production. Having 3 pieces with a period spanning over 12 years means there should be plenty of these.
If this were merely a fake product, would the forger not try to make his fake binocular look exactly like the original? I would imagine they would put Carl Zeiss logo and make sure it looks as identical to the original as possible, wouldn't they?
I looked through magnifying glass at the surface where the logos are, and did not see any trace of erased engraving: it would need to be erased quite deep I guess. However, I am not 100% sure, because the area on which the logos are is more matt than that closer to the edges of the metal plates. It could theoretically be that someone removed the original engravings, added paint, polished it and then engraved new logos. Not sure if this is possible - because the engraving looks perfect quality and must have been made by a machine, not by hand. And again, why to alter by removing Carl Zeiss logo the presence of which makes the binoculars more not less valuable. And I do not have other binoculars to compare - maybe the middles of plates with logos are always matt and the edges are shiny because they get overtime polished by the hands holding the piece.
Overall, it looks a good quality piece, not a cheap product. Can it be that the factory was for some reasons producing certain number of items a year for a country or an organisation that could not use the Carl Zeiss product. This is as I understand your recent suggestion, and I tend to think the same way.
Thank you very much for looking into this. Let us see and maybe more people would post pieces like this or provide inputs on possible origin.
Whatever it is, fake or genuine, the time spent on trying to identify it is so exciting!