Thanks for the responses... I just measured one of the old dirty springs. Measures 3/4" wide and 108" long. I don't know the thickness (strength). I see that Timesavers has both a 3/4"x.014"x108" and a 3/4"x.016"x108" spring available. Since the movement uses both springs to drive the time-only gear train I am thinking I should go with the .014" thick spring?
Yes, what Harold said. I had assumed the springs were missing. If the springs have a rough and mottled appearance, they could be wrought iron springs. Wrought iron springs are by nature thicker than modern springs but not stronger. I do not usually replace them unless they show cracks or rust.