IWC Strap Alligator Marron Light Brown For Pin Buckle (IWE03157) This luxurious IWC Marron light brown alligator leather strap in regular size is suitable for use with a pin buckle and can be worn on any IWC Portofino 37 Ladies watch under reference IW3581. If you require any assistance finding the right strap for your IWC watch, you can fill out our strap finder form here. A member of the Jura Watches team will get back to you as soon as possible with some options.