Some color from my Kodak Retina IIa.
I have five different models from Kodak's line of Retina cameras. All are excellent shooters, but the IIa rangefinder model if my favorite because of its high-quality construction, compactness and reliability. The lens diagram below illustrates the IIa lens, the Schneider Xenon 50mm f/2.0. As shown, the lens consists of six elements in four groups, arranged symmetrically around the shutter. It was easily equal to anything in its class when introduced in 1951.