In good working condition (see video) I don't know how to open this particular pigeon racing clock but my understanding is that  the pigeons return from a race and and the identifying metal ribbon/bead on it's leg is removed and placed into the slot on the top of the clock and the switch on the side of the clock is clicked and this sweeps the bead into the clock where it is held in a numbered compartment as proof of the order of arrival of that bird. The bottom paper disk does tick and spin I'm not sure how to wind or operate this piece but it appears to be in good working order. Measurements with the clock in it's wood case 9." high x 9." wide x 5.5/8" deep. Weight 9 pounds 14.7 ounces. Please view all photos with care. See images with ruler for scale.