Rapid-Omega Lens Design Roundup
Having noticed that both my Dad's Rapid-Omega and my Mamiya C330 had nearly identical 180mm f/4.5, but that their size differed, I got curious about the pedigree of the Rapid-Omega lens line.
Didn't take me too long to figure out that most lenses were in fact versions of classic Zeiss designs (Biogon, Tessar, Planar, and maybe Sonnar), and that the RB and Mamiya TLR systems also shared nearly-identical lenses with the Omega system.
So for your reference and amusement, here's my chart identifying the various lens designs. The only one I'm not sure is the 180mm: it looks like some kind of Sonnar, but it surely isn't typical of classic Zeiss designs.