assuming its the ƒ5.6 version? (I've seen an ƒ6.8 version as well.) I don't know this lens specifically, but many of the Caltar lenses were rebranded Rodenstock lenses, so my guess is that this is a Sironar of some vintage or another. If so, then its a modern plasmat, so should have a high quality image. I find plasmats at that focal length or longer are a bit heavy for my taste, so I shoot a Xenar 210mm ƒ6.1 and a Kodak Ektar 203mm ƒ7.7 which are both much smaller and lighter.
In good shape, with a shutter, its probably a good deal.