Assuming that a lens with such a name should work perfectly with the two elements together (so at least the first 100 $ are well spent), I agree completely with Sean Yates, expecially for the possibility of having a TRIAL PERIOD to be able to test the various combinations when you want to use only one group (placing it before or after the aperture iris, with the convex side in the direction of the film or of the subject etc.etc.) I have a Zeiss ProtarLinse series VII made in the year 1923 which performs extremely well using the two elements together (focal lengt about 210 mm) and gives good results even with one group only, but my judgement is also related to the price I payed the lens: $60 in the fly-market of Rome!