Walter Degroot , Jul 23, 2008; 06:28 p.m.
it does say CS, I thoughtb you were talking about the YS lenses, which were compatible to T and T2, but had auto diaphragm. I see from the photo that there is, indeed, a difference the YS lenses were sold by spiratone as accura diamatic, Often or usually made by sigma. they were also sold as several other brands including Cambron, ( i hesitate to mis-spenn the other names)
I read that later FIXED-MOUNT sigma lenses were actually YS lenses and the mounts could be changed.
I do not know how to is these lenses.