I have a Retina IIIc that I got on the "Bay" a couple of years ago. This camera was built in the mid 50's and in nice condition.
I did have some issues with the rangefinder on it, but with information found on RFF, I was able to fix it. This is a very nice, well built, precision piece of equipment and probably a little more complex than other quality cameras from the same era. The f2.0 lens is quite good and I was quite pleased with the recent photos that I took with it of my grandchilren.
When folded-up, it's very compact but being solid metal, it is quite heavy.
I bought it because it was a piece of history and I believe that at it's time of production, it was considered to be second only to a Leica in terms of quality.
These are just my feelings on the Retina. I like mine and play with it frequently.
Best regards,
Bill K.