If it does not have a lens board, measure the size of the opening to see which size lensboard you need. You can check the SK grimes site to see if those dimensions match some other maker's boards. Otherwise you can make your own out of model aircraft plywood or aluminum. Don't cut the hole in the middle until you get your lens. Look for a 240 to 360mm lens in a Copal #3 size shutter. I don't know of many lenses in #3 shutters that DON"T cover 8x10.