Paul Landenberger, who was born in 1848 in Ebingen (Germany) and 1939 died in Schramberg (Germany), was employed from 1868 at Junghans than being responsible for the purchase and distribution of watches of American production.
In 1871 he was elevated to the technical director of the company Junghans and married a year later, the daughter of Erhard Junghans (he died in 1870) named Frida Junghans. Dissatisfied with the nonexistent chances to climb up the stairs in the company, Landenberger emerged in 1875 from Junghans and founded the company Landenberger & Lang and thus became a competitor for Junghans, especially since he still resided in Schramberg and he also still took many employees from his former company.
Forced by financial difficulties, he had to ask for a loan even at Junghans. After another, even legal disputes with Junghans finally a settlement was reached in 1883 and the original company Landenberger & Lang was converted into a corporation named "Hamburg-Amerikanische Uhrenfabrik (HAU)". Landenberger apparently had good relations with the company Deuerer & Kaufmann in Hamburg, that probably earlier sold its watches. Landenberger still remained in dispute with Junghans, whether for family reasons or because of disputes about markets is unclear.
In 1925 the number of employees of HAU was approximately 2,200 people. A key product of HAU were the ATO clocks whose license was acquired in 1929 by Haller & Benzing after their closure. Forced by the losses due to inflation in 1925 a community of interests between Junghans, the Vereinigte Freiburger Uhrenfabriken and the HAU founded in 1927. The plan to grow stronger economically was braked abruptly by a massive loss of equity of the companies involved. Finally Junghans took over the other two as the strongest company in 1930. Paul Landenberger became board member of Gebrüder Junghans AG. In 1939 the name "HAU" no longer performed.
The HAU was mainly known for the production of alarm clocks, and small clocks for tables
Only for a short time (how long exactly is unclear) watches with both names (Junghans and HAU) were produced.
In addition to large watches and alarm clocks, wristwatches with movements from Junghans were also sold with the factory brand of HAU (or H.A.C. = Hamburg American Clock Company; for the English market).
In 1956, Junghans registered the two crossed arrows as trademarks.
The watches marketed with H.A.C. can usually be found on the English market. The caliber Junghans J97 used by H.A.C. is very rare to find. It is the variant with 7 jewels and stone lever movement, on the dial are the watches with the arrow cross drawn, including H.A.C., under the 6 "FOREIGN". Also on the movement the well-known "FOREIGN" can be read beside the 8-pointed star and the "J" with "unghans". A little more frequent are watches which house the Junghans J80 or Junghans 680.70, here you can find watches with different case diameters.