Interesting history behind this piece. As you can see, the design is quite reminiscent of the Navitimer made famous by Breitling starting in the 1950s -- click here for a comparison. Well, the Sinn Navigators actually can trace their horological DNA directly to these original Navitimers (quite unlike modern Navitimers by Breitling).
In 1979 Breitling went bankrupt and Willy Breitling sold off all the assets of the company bearing his name. Ernst Schneider purchased the rights to the "Breitling" and "Navitimer" names along with several other famous Breitling trademarks. At the same time, Helmut Sinn purchased the rights to the Navitimer watch design, tooling, and all remaining parts inventory.
Sinn would go on to refine and enhance the Navitimer design thru the years under the Navigator name, using Willy Breitling's original design as the basis. Sinn's development of the Navitimer/Navigator design was not limited to the Lemania movement you see in this example. Through the years, Sinn Navigator designs included variants powered by: Valjoux 7740, 7750, and Lemania 1872, 1873, 1877, 1883, and Excelsior Park 40-68.
Schneider would create a new company under the Breitling trademark and develop an incredibly diverse array of new Navitimer designs that continue to be sold today.
