I think the 11a is the best of the Retina models.Some of the earlier models didn't have the rangefinder.They added selenium metering to later models, but most of those selenium meters have died by now, and even if they're still going, I'd be loathe to trust the accuracy. They also made some later none folding Retinas of the same build quality, but Im specifically after a folder
Both the Voigtlander and the Zeiss Ikon mentioned earlier are even better build quality - both gloriously over-engineered in fact, but it's the Retina which appeals as relatively quick to use and the one I'd enjoy shoving a film through now and again.