If you want to get really fancy you can look for six-eye monos and six-eye stereos. red label with black eyes on the monos, inverted on the stereos. I'll second Narrod that the two-eyes are hit and miss and the later no-eyes and everything else are very hit and miss from a quality perspective. Its unfortunate too, because Columbia's recording facilities delivered some really great sounding records - Kind of Blue, Time Out, etc.
