Tom- just for some perspective on marks in the glass, if you dig through the archives here, a few years ago Jim Galli started a thread about a Cooke portrait lens he bought. It was a rare lens, worth multiple thousands of dollars in good condition. This example looked like someone had hit the front element with a sledgehammer. Literally, a forking crack the whole way across the front element. He shot it for giggles, and other than some contrast loss, it produced good images. So a little nick in the rear element won't do jack to an image.