A black marble perpetual calendar mantel clock, Jean-Baptiste Delettrez, French, circa 1870

5½-inch two-piece enamel dial with visible Brocot escapement, jewelled pallets and centre seconds, the bell striking movement No.28665 signed Wm.Roskell & Co. 21 Church Street, Liverpool and Paris and stamped JBD for the maker, a lever leading from the strike  train to the calendar movement indicating month with equation of time, date, day of the week and moon phase, the Egyptian inspired case with a shaped glazed panel at the centre revealing the Ellicott-type pendulum flanked by a metallic barometer and the calendar dial with Fahrenheit and Reaumur thermometers above, the incised mouldings gilded