1931 - 1953
J48, J48G, J48b/1
F.W.S 1942 page 18
According to a letter from Friedrich Emmel to Mr. v. Zeppelin, 28. April 1958, the construction of a new pocket watch with a quality between J38 and J41/J42 was ordered in 1928. Result was the J47, J48 and J49 which could be delivered 1930.
Junghans catalog 1931 text:
Second adjustment. The watch to be set exactly to the second.
Bridge movement, flat, 15 jewels, flat hair spring, lever escapement with visible jewels, double safety roller, gilt plates and bridges.
G indicates a new click spring assembly from 1934.
The suffix /1 means that a seperate escapement wheel bridge/cock is used.
I assume that these watches are made from 1938 or later.