An Optional velcro strap in black or grey was available – these straps hooked up to the main male website link with the bracelet. Thankfully, the fabric strap with the IW3715-36 and also the alternate rubber strap within the IW3548 match the Aquatimer! Christie’s This was mainly a ref. 6538 https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/