Tim Eck is right that it is not easy to abuse this kind of scope with ordinary care, but if it was used in a microlithography lab where they etch silicon wafers with hydrofluoric acid, there isn't an unetched piece on the scope. And student scopes have the damndest things done to them. --Ellen C. -- Dr. Ellen Chernoff, Ph.D. Associate Professor of Biology IUPUI-Biology SL 360 723 W. Michigan St. Indianapolis, IN 46202-5132 317-274-0591