Okay, dumb question. What is a boss? I read something a couple of days ago and now I can't find it. I knew I should have paid more attention to that. Here are a couple of photos of the Kohler. There is a hole in the center of the balance wheel that is threaded. Also, look at the top photo of the Tryer at this website. This machine looks very much like the one I have and the photo shows a hand crank on it.
http://www.sewmuse.co.uk/Kohler%20sewing%20machine.htm