I have a couple of Georges Favre-Jacot (Zenith) pocket half-chronometers, cal. Billodes 19'''-54, 15 and 23 jewels, open face and hunter silver cases. As far as I know they were made for the old Russian market. Does anybody know another models of G.F.J./Zenith 1/2 chronometer? I didn't find even a such type of watches in Manfred Rössler's and Joël Duval's books.