Paul,
I guess it's a matter of how far one goes back. The first attachment shows a 1965 Audubon with your Holiday on the computer screen in the background. They are the same mechanics, but only provide a measly 3mm more eye relief. Still, it works to a degree. The second attachment shows the
original 1958 Audubon in the foreground, which may or may not have had a removable eyecup (I think it did). Behind it is the 1959 model with a bayonet mounted removable eyecup placed on the left cover plate. And finally, the 1965 model as seen previously. The FOV of these specimens, incidentally, was 420 ft. for the original 1950 models, and 445 ft. for the 1965 model.
Note that it only took one year to evolve to a bayonet mount and at most seven to evolve into a twist-out eyecup, which is not too dissimilar to modern roofs.
Ed
Ed
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