<p>I can't imagine a better 35mm folder than my Retina IIIc (though I haven't used a lot of others, so take that with a grain of salt) -- it's a joy to use, and the lens is fantastic. Any of the Retina folders with a rangefinder should be great users though -- which means any of the II or III models, I believe. If you don't care about having a light meter on it, which may or may not work anyway (the meter on mine happens to work and I use it), then maybe go for a II model and save some money. I have a couple of Retina IIa folders that I've been doing a little work on, and the biggest difference I see is the solidity of the whole lens/shutter mechanism on the IIIc compared to the IIa. On my IIIc the lens is rock solid and steady, but the IIa has a bit more flimsy build in the slide-out lens mechanism. It might be that these particular copies of the IIa are more worn out than usual, but the build of it makes me think this might be typical.</p>
<p>I also have a Zeiss Ikon Contessa, which I absolutely love the look of but don't find it as easy to use as the Retina. It spends more time on the display shelf while the Retina IIIc might be out being used. </p>
<p>p.s. - I'm sure some would disagree, but I wouldn't pay the extra premium for the 'big-C' Retina IIIC model. </p>