No, you haven't ended up at the wrong site. While there's a case to be made that John Belushi's character in "The Blues Brothers" is a chosen favorite of Nyarlathotep, the film isn't something that falls within the normal purview of Propnomicon. Except in this case, it does.
Two years ago I stumbled across an interesting "Italian wooden space helmet prop" being offered by the Blackman Cruz design and decorating firm. It allegedly dated back to the 1930s, but bore a striking resemblance to some of Ralph McQuarrie's concept designs for the stormtrooper helmets in "Star Wars". Given the rabid community of fans that microscopically study every detail of those helmets I thought it was amazing that no one had ever remarked on the similarity.
Last night "TK826" left a comment on the original post about the helmet that points to this still from the making of "The Blues Brothers". It's filled with vacuum formed casts from the "1930s Italian space helmet prop" master, presumably from a toy store in the mall rampage sequence from the film.
The picture doesn't prove the Blackman Cruz helmet isn't from the 1930s, but I think it's pretty strong evidence in that direction. To date no one has ever identified an Italian film from any era featuring that particular helmet design. It seems far more believable that the master was produced in the late 1970s by the prop house providing set decoration for "The Blues Brothers" and was intentionally patterned after the McQuarrie designs. An intriguing alternative is that it's an actual master from the pre-production period of "Star Wars". If that's true there's someone out there who thinks they have a pricy objet d'art sitting on their tabletop, when in actuality it's a prop master a "Star Wars" collector would die for.