I have some new old stock 1960s/1970s Swiss Genuine Perlon 2-piece straps with double keepers and heavy-duty buckles. These fit 11/16″, 18mm, and 19mm. Watches shown as an example of fit. The Yema Superman, Alsta Nautoscaph, Wakmann Skindiver, and Aquadive 1939 shown below are 19mm spacing, the …