Those are some great pictures, for sure.
Dig,or anyone, on the facebook link picture #3, Woodward bar lock # 4209, there a little raised square filed on the internal side of the upper arm of the mainspring near to the bend.
I always imagined that the main spring anchor pin in the bar of the action was filed from a nub left on the spring & filed to make the pin?..or did they drill a wee hole through the spring for a seperate pin & this is a kind of bolster to add more strength?
The little square bit is right around the spot were the pin would be, thats what made me think of the latter idea...though wouldn't that weaken the spring?
thanks
franc