Ilex 7.5" Paragon lens, missing rear lens cell? Was someone using it as a convertible lens?

So, I bought this lens and shutter just for the shutter. I got a nice looking Ilex 7.5" F4.5 Paragon and Ilex #3 Acme Synchro for what I considered to be reasonable money, but while the front lens looks pretty good, the rear lens cell is completely missing. Now, I was not looking for the lens here-I just wanted the shutter for parts.

The shutter has had a dual aperture scale fitted. Is it likely that someone had this lens and shutter re-scaled for use as a convertible lens, and the rear cell is missing because it's now set up as some other focal length? One aperture scale runs the full swing of the aperture control lever, going from F4.5 to F45, and the second scale runs from F4.5 to F32. Scale 2's F4.5 mark falls between Scale 1's F5.6 and F6.8 marks, and the F32 mark matches up with Scale 1's F45 mark.

Again-I was just interested in the shutter, but now I'm intrigued by the possibility that someone was doing something neat here.

Hmm. F/4.5 Paragons are tessar types, are not convertible.

A convertible lens' cells maximum apertures are typically around twice the whole lens' maximum aperture.

Ilex made a 6/4 convertible plasmat type, usually f/4.8 for the complete lens. Usually badged Acuton, sometimes badged Commercial Paragon. I take it that your lens is engraved "Paragon."

The shutter's aperture scales are for two different f/4.5 focal lengths, not for a convertible's single cells.

I thought that all the Paragons and Paragon Anastigmats were Tessar-types, so that's why I was curious about why someone might have done that intentionally.

I also have an Ilex Seminat in a #3 Synchro, which functions but is 1 to 2 stops slow on all speeds. Hoping that this one comes in closer to indicated speed, and I can send both shutters out for maintenance.

I can find almost no information about the Ilex 6" Seminat, although mine appears to have been single-coated at some point-the coating (or maybe just a layer of schmoo!) is coming off the rear element.

I don't know much about mechanical design of Ilex lenses, cells' threading in particular. My best guess about your shutters two aperture scales is that its owner wanted to use two lenses, longer and shorter, with it.

I don't know why they do it, but sellers on, e.g., eBay sometimes offer single lens cells, usually front cells, by themselves or in shutter, as complete lenses. I've stopped buying lenses but I still look at lenses from aerial cameras offered on eBay. Too many of them are front cells, not complete lenses.

The Seminat is pretty much a mystery.

After I get the camera together and working, I have considered sending this Seminat to a guy who apparently will do lens cleanings and coatings for photographers, and asking if he'd disassemble, clean, and document this thing so we could know.

I could disassemble and clean it but I do not have the expertise to tell anyone what I see when I get it apart. My time working for an optical company was long ago and all I did was PVD coatings.