A new old stock BWC chronograph watch strap. Each of these has differences due to the calf grain. The strap has 20mm ends, takes a 14mm wide buckle (the one supplied is the manufacturers gold steel one) and is 11.5cm 7cm in length not including the buckle. The same design strap can be seen on vintage advertising material for BWC chronographs in the 1960s and can also be seen on this example here.
