As per ASME B 40.1, pressure gauge ring is defined as the component that secures the window to the case. Event though it will be vary from one vendor to another vendor (due to their specific design and aesthetic view) we shall mentioned it clearly in the datasheet.
The choices are screwed ring, hinged ring, slip ring, and manufacture standard. If we specify it shall manufacture standard, it means we accept any manufacture standard design as long as another specification is in compliance.
Screwed or threaded ring are a ring that have a threads match with the threads on the case. Hinged ring are a ring that retained by a hinge-type device and a single retaining screw. Slip ring is a ring retained by means of interference or friction fit between it and the case and also it has a clearance fit with the case and is secured by screws.