Small Swiss chess clock, manufactured based on the Birse-Clock-Court J.B movements. Birse Clock Company registered its trademark on 7 March 1944, thereby chess clocks started appearing on the market in the early post-war period. Swiss movements contain 4 jewels and are of a very high quality. Advertised in the Swiss Chess Magazine in 1948. Earliest available evidence of the Birse tournament usage refers to the International Christmas Chess Tournament (Lucerne, 1948), however it’s most famous coming out is definitely 9th Chess Olympiad in Dubrovnik (1950).