DENT 1973 CONGREVE ROLLING BALL CLOCK./ The gilt brass movement of this clock opperates by a rolling ball which runs down a zig-zag track, where it trips the escapement reversing the tilt of the tray, at the same time causing the hands of the clock to move forward. Has hour, minute and second silvered dials. The original concept design of this clock was invented by Sir William Congreve in 1808. This clock used those original concept drawings and was made by Dent, in 1973. The back of the movement reads - Andrew Fell - Del. 1973 - Ser. No 132. 19"W x 17.5"H x 14.5"D.