Hello, Could anybody tell me more about this lens. I've looked at the postings in the a rchive, and none seem to have the answers I need. This lens says Schneider Corp. of America in front and is mounted on an early Co pal 3 shutter. It's made in Switzerland, by Kern I believe. How does it differ to the ones with a Compur 3 shutter that says Schneider Kreus znach and MC in front? Is it just different vintage? Do they perform and cover similarly? What would be the most practical way to att ach filters, the lens is unthreaded? Thanks, and good shooting.