Types of Case Backs
This is a picture of the brochure that came with the Bergeon case opener 5338-1 F, the copyright belong to the company Bergeon, Switzerland. I hope they do not mind me using it without their permission. At least I advertise their products here, so I hope they will be mercyful.
The tool on the top is the Bergeon 5338-1 F which I bought to finally have the right tool for older polygonal case backs (Double Rhomb, Borel). Also the Meikosha 19400 actually works great on octagonal watch cases. I bought less expensive but excellent opener for my Hong Kong watch tool box.
The bottom tool is the Bergeon 5337 that comes with 6 dies fitting most Rolex and Tudor cases with grooves.
Top row from left to right: Cases with holes - Cases with grooves (Rolex) - Aquastar cases
Bottom row, left to right: Cases with slots (most popular today) - Polygonal Cases 12 and 8 edges