FEF 21.5" Dual Time

duplex escapement for jumping second (Fig.3) Due to one pair of rest teeth for each pulse tooth, the second hand changes between a hardly visible step and about one second, thus appears as jumping second. The balance gets only each four beats (once per second) an impulse. It doesn't self start (like in every duplex escapement); the movement neads a twist motion to start. bimetallic screw balance, not cut barrel stop-work cf. Fleurier 21.5" indirect sub second, driven by the escape-wheel pinion direct sweep second