1948 Eska Chronograph, military style big 37.2mm case, patented caseback waterproof looking system and Chrono pushers that I never seen before.
Eska was one of the smallest watch brands in Swiss. After the end of World War I, many watch manufacturers appeared in Europe and Sylvan Kocher & Cie. was of them. The name Eska is the phonetic spelling in French of the letter s and k (es-ka). The wristwatches of the brand included manual and automatic models, besides models with full calendars and digital time displays.