Well, I would first of all try and match the original so that you have two
projectors with exactly the same lens, and one isn't brighter than the other
or have slightly different color or distortion than the other.
Eiki takes the same 42.5mm barrel lenses that Bauer, Philips, Kinoton,
Seimens, and Meopta projectors take. Any 1-inch 42.5mm lens will work.
If you have a lot of money you could buy two brand new Isco Ultra-Stars in
that format. Or you could call MTE in Florida and see what is on their
used lens shelf. But I would make sure to get two lenses that matched.
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