Quote Originally Posted by safeman View Post
Thanks for that Tom, I never thought of a day lock which I've only seen once before and that was on a huge Milner in the City Collector's Dept. of the Glasgow Corporation. It was a spring latch which I assumed to be an emergency closure device against hold-up.

I'll guess that the top left handle is a pull handle and top right the keyhole shutter knob with the cross-locking bars round handle below.
The pivotting seesaw has connections to the safe boltwork on both sides of the lock - that is thrown by the drop handle while the central knob is for moving the bolt stumps into the fan levers