I've mentioned this elsewhere, but there is a story/legend that the Tessars used in the T Rolleis had a lanthanum element to improve corrections. I do know that that Tessar is a wonderfully nice lens, one of the sharpest lenses of any type I've ever used. I currently have a Standard, with an uncoated Tessar.
Originally Posted by Dan Daniel
Another point worth making is that it is essential to be sure your Rollei is properly aligned.