Was there ever a 90mm M Noctilux?
Yes! Believe it or not a few 90mm M lenses with a minimum aperture of ƒ1.0 were actually made in the late 1960s. As David Young noted on a mailing list in September 2000:
Jim Lager's Illustrated Guide III (page 44) shows an Elcan 90mm ƒ1.0 made in the late 60's for the US Navy. Special extension rings fixed the focus at 50, 100 meters and infinity rather than having a standard helicoid mount.
About 500 Elcan 50mm/2's were supplied with a special version of the M4 (KE-7A) but a 66mm ƒ2 and 90mm ƒ1.0 were only made as prototypes, and never produced in any quantity.
You can also find a small photo of this glass monster at p.234 of Popular Photography magazine, volume 64, no. 6, June 2000. It's shown mounted on a M2, and the diameter of the front element is almost the same width as the M2 body… Yikes!