I already have a 210mm Sironar-N MC, a 215mm Series-S Ilex Calumet, and a 8 1/2" Ross Homocentric. The I-51 would be more to just add to the collection than as a "real" user. Besides, the sharper or contrastier lens isn't always the best choice! (especially when shooting people)
Oh dear! Another person afflected with Tjugen's Syndrome.
It's apparently an abbreviation for "Weichzeichner" meaning "soft". It's a simple "periskop" type lens - two simple meniscus leneses symmetrically placed around the stop. The aperture is marked in millimeters, not f-stops. It may have been made as an enlarger lens, although it's hard to understand why anyone would want a soft enlarger lens?
Anyway I'm going to try doing portraits with it...