WoW! you are SO lucky on the New National!!! Those are fragile to begin with... I had one and traded it to the local Cathy since it was a 1920's production, but it was a smooth machine for the lower end of the market.
Removing the remains of the handle screw should not be TOO bad... (not fun, but...) Once you have the thread size, length, etc, let me know. If I cannot find one, I can make one.
EDIT: I am pretty sure that the Leaf tension was the later version. This Version is very similar to the Howe B tension (and shuttle)
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Last edited by SteveH; 07-22-2015 at 02:57 PM.