...so, yes, thanks, Dan. http://www.galerie-photo.com/ilex-lenses.html
The optical design across its iterations over the years is said to be identical. They came in a variety of shutters (Ilex, Compur, Seiko, Copal (0 and 1),...) and there are also versions without filter thread (!), so it makes me wonder if they didn't have, even minor, optical updates as well during their run. Another comment: My copy opens up to about f6.8 or thereabouts, both the shutter and the lens are marked f8; so, although noticable, its only really a stop slower than the f4.5 for preview.