After I uncased the watch, spun the balance wheel and rotated it from DD to the DU position, I not only saw the balance staff fall, but I could hear it as well. Obviously, this caused the balance wheel to stop. It looks like David hit this on the head in the last post. There’s just too much end shake.
My next step is to pull out the balance assembly, remove the top and bottom cap jewels, and caluclate the required balance staff length. For those who might be interested, I will be referencing Fried’s book, The Watch Repairer’s Manual pages 126-128. When I measure the actual length of the staff, I expect that measurement to be less than the calculated length.
Any other thoughts?