from what I just read:
Caltar II N 5.6 = Rodenstock Sironar N 5.6 (made by Rodenstock)
Caltar II S 5.6 = Schneider Symmar S 5.6 (made by Schneider)
Rodenstock Sironar N 5.6 = itself
You sure don't need all three. Try 'em all, see if you can see a difference. Keep the one you like best (if you can tell the difference).
I had an old (1960's) Symmar that I never cared for. It had a bit of softness that I wasn't expecting - large bubble in the internal cement. I got rid of it, Marsha Burns ended up with it and I heard she loved it. Don't know if she still uses it. If so, I'm sure it's making beautiful images. I have a Sironar N, which I really like. You might do some research on them. Differences will be minimal, and may actually be less due to the name/maker than variations in individual lenses. If you really are picky, check and see whether they are single/multi coated. Myself, I don't much care for multicoated lenses because they can be unkind to the shadows. So much of this is personal preference and most people probably don't have the capacity to distinguish such subtle differences.
If they were mine, I'd want to unburden myself of 2/3 of them. Too confusing. You could draw straws.