RARE Antique, Scientific Experiments Interval Clock for Arthur W Hall, Boston

……. It took a search on the internet to figure what this one hand clock was used for. Marked on the dial, “Interval Clock, Made Expressly for Arthur W. Hall Scientific C. Boston by S.E. Thayer, Westfield, Mass” this Scientific Laboratory Clock is quite rare. In fact I could find only one other example and it was at The Museum of Natural History. … Measuring 8 ¾” tall with a 3 ¾” wide base this nickel plated clock is 4 1.8” in diameter by 1 ¼” wide with a 2 3/8” diameter bell. On the back are directions on how to use this Interval Clock. The main spring is would tight, and when a give the clock a slight shake it runs for about 20 seconds and then stops. The only other problem is the original glass which is slight loose.