Junghans J5, updated 12.09.2020
Junghans
Alarm pocket watch
1906
1909 - 1913
Open face
J5
21'''
48,1 mm
9,7 mm
18000
24 h
U1060
W1071
Zf930, 620 x 2,7 x 0,24 mm
Jacob 1948 page 90
50 x 83 mm
135 g
60 g
3/4
Schramberg
48°
This is the J5 alarm pocket watch made by Junghans. It is a 21''' movements with 3 jewels, lever escapement with visible jewels, brass escape wheel and a flat hair spring.
It appeared for the first time in the 1909 Junghans catalog. The last known catalog entry was in 1912. The J5 was replaced with the J10 movement in 1911. According to a Junghans list the J5 was developed already in 1906, production came later in 1909 which can be validated by the catalogs and corresponding contributions in the "Deutsche Uhrmacher-Zeitung" and "Leipziger Uhrmacherzeitung" in 1909. J5 is mentioned in the Parts-pricelist Nr. 515, 1913 together with the J10.
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How to seperate J5 from J10 and J36.
Part chart from 1913, courtesy of JUNGHANS GMBH & CO.KG
From the "Leipziger Uhrmacherzeitung" Nr. 8 1909
My free translation of the article:
Pocket alarm clock
For some time now the united watch manufacturers Gebrüder Junghans and Thoms Haller AG fabricate in Schramberg a pocket alarm clock, which has proved to be very practical. We bring alongside a rear view of the work, in which the bell is removed and add the following comments: 
This clock must be treated in the same respect to their function as timepieces exactly as any other pocket watch. The winding is done by turning the crown, the hands also by turning the crown and the simultaneous pushing the pin located above the 1. Because this is an alarm clock pocket watch, the time pointer may only be moved forward.
Above the 11 there is a second pin and it depressing the alarm pointer is advanced. Repeatedly pressing this pin will advance the yellow pointer to that time at which you wish to be woken. Thus, the bell sounds good, the lid of the case has to be open and the clock must be set up. The bell has a small slot through which a lever is visible. Depending on this lever is set to "wake up" or "silent" is set, the alarm clock does occur, or not. If the clock does not wake up, you must check whether this lever is properly set. The pocket alarm clock can not only wake up in the morning, but also set at any time, be carried in your pocket, where the carrier will be reminded to his special intentions of certain time. This pocket alarm clock comes with enamel or silver-plated face in nickel or steel housings, as well as with illuminated face. For the latter an approximately ten times more luminous material is used as the known Radium-Darling alarm clocks. Therefore, the clock lights already in at dawn and the time can be read even through a thin cloth into the darkness. However, this face is increasing the price of the alarm clock by 40%. Movement and case are Schramberger brand. It was a great series of machines and equipment according to the latest experiences built and purchased. The second variety of these watches will also come with four jewels, after the first one is now sold out.