greywuuf, that top piece is pretty big to be a sprue for casting...and while I can understand your theory because of my study of cast iron cookware, I don't believe that this is a sprue. I've yet to see a true sprue on a sewing machine, due to the large "underside" of the machines, it would not have been necessary, nor would it have made sense, to pour from the top of the machine head. Even the oldest of machines don't have a sprue on the top side of the machine that I've seen.
Interesting theory tho, and one that bears more investigation!
