[ithacaartist]

Bill,

I believe that the original intention of the toggle lock was to prevent the action from unlocking once it has slapped into battery during a cycle--this, due to potential bouncing of the parts. It was found to be unnecessary, however, because in practice, this basically didn't happen. The 1906s were built without this unnecessary little system.

The toggle knobs of the 1900 need to be drawn back a little differently than those without the lock, whereby the knobs must first be drawn directly rearward until they move from under the lock/latch on the frame.