Charlie -
Thank you so much for the wealth of information about the 240. I will work to try to find a cross-reference sheet to determine the modern-day equivalent of the the electric eye battery. In the manual, it also calls for a Mallory-type battery - I don't have the manual with me right now, so I'm not sure which model of the Mallory battery.
All of the information regarding how the electric eye functions is extremely helpful. I was working with the camera the other day, and tried to move the f-stop ring manually, but the ring is really stiff on the camera and barely moves. Perhaps I'll need to get this serviced at some point, because I'm sure the camera hasn't been lubricated in decades. It was stored in good conditions, however, so everything is in really good shape - nothing's rusted, etc.
Thanks again for all the information. I appreciate it!
Jay