Two Zips

'Conventional zip fasteners are not really tough enough for Billinghams’ standards. Therefore, they use strong 8mm zips, where the coil teeth are sewn into the supporting tape. Not only is the resultant fastener stronger then a conventional zip, it is also flatter and less prone to abrasion. '
Billingham bag photographed with a Micro-Nikkor f/3.5 55mm AI on a Nikon D2Xs.
Gideon Sundbäck, who was born in 1880, invented the zip fastener.