It was a tiny bug. Crawling about inside the of the optical pentaprism chain. How it got there, I am clueless--but the extraction job involved looking at everything. One of the first things I noticed was that there was an easily accessible metal bail holding the focusing screen in place. Frankly, I have never liked a solid matte screen--and research, when I got the camera several years ago, did not indicate that there were any choices. Imagine my surprise when I found that a quick push with the roach clip (err, I mean hemostat ) dropped this little gem in my hand. A quick bit of research on the innernutz showed me that there were MANY possible replacements--ranging from actual ground glass, to split and microprism ring configurations! I note that there are ordering options available--ranging from fleabay to Taiwan direct. Have any of you had experience in adding one of these--and recommendations? I think that I want the split center and a microprism ring.