Mechanical Prosthetic Hand, c. 1910, Carnes Co. USA.
The grasp of the fingers is achieved by using a short steel worm to rotate a sector rack. This ensures locking of the fingers at any diameter (as a rack can’t generally turn a worm). The leather cord is attached to the worm diameter at the cords mid point giving two ends. Pull one end to rotate worm and unclasp fingers, the other end to clasp. The action sounds a lot like cocking a rifle. The cord should be 4 mm leather cord. The materials are a poetic combination of alloy palm for lightweight, steel fingers for strength and wood finger tips for warmth of touch. There’s more info on the example in the Smithsonian Museum on their website.
*Sold complete with the arm and integral wrist mechanism it can also be displayed in the context of an automata collection as the hand alone under a glass dome, upright or in the writing position on a velvet pad.