Carton for a Junghans stopwatch from WW2. Stopwatches like that were used for example for calculating torpedo timing and measuring time to impact by U-Boot officers. 
The dimenstion of the box are 60x60x22 mm. The diameter of stopwatch in pictures (not included) is 49mm.
 
Note: as the product is not flat, it requires "rigid envelope" shipping for the USA, or "tracked international package" for other counties.