The Junghans 671 (J71) is available in two versions (15 and 17 jewels), each with two different movement heights.
In the thirties, the caliber designation J71 was already used for a 17 ''' pocket watch-caliber: Junghans J71 - pocket watch
Further information on the pocket watch caliber Junghans J71 also on the website of Dirk Fassbender: http://www.dirkfassbender.de/Junghans J71