Designer engagement rings - What`s the difference?

On the other hand what defines designer jewelry and how much of a deviation from an existing design, for example classic solitaire, constitutes new one. There is no base for precise classification of design changes and the definition of some terms often used in the jewelry industry presented bellow is my own.
The term Designer Jewelry should be applied to pieces representing individual style a particular designer is trying to promote. In engagement ring field this style is usually defined by using certain unusual technique (mokume, granulation), unusual way of setting the diamond/s, specific recognizable shape (organic , geometrical), unusual metal alloys bringing new color or mechanical properties,  unusual surface texture and many more. The common denominations are unusual and recognizable. I believe that there is no need for major change to constitute designer engagement ring. The famous Niessing tension set ring for example is nothing more than a excessively thick comfort fit wedding band with small sector cut off to accommodate (clip) the diamond. It is still considered however as one of the greatest jewelry designs ever and sold by thousands every year. Sometimes the designers touch is hardly noticeable at first glance especially when applied to classic rings. Tapering the prongs and increasing the angle of the basket of a classic solitaire for example, creates much lighter and open setting while the thicker metal at the top offers superb safety. Such small change however creates very elegant design line and significantly improves the overall appearance and safety of the setting. When asked for an opinion the customer usually answers: “It definitely looks different but I don`t know why” 
Designer diamond engagement rings are not necessarily unique and are reproduced in relatively big volumes. This makes them different from the studio and ones off pieces. With the studio type jewelry, the designer is the goldsmith and gemologist, executing his / hers pieces from A to Z and once off pieces are the bulk of his/her work. These are still not unique though, since most of them are reproducible by the same artist but they are definitely a limited edition. Limited editions and once offs can be clearly separated by natural and intended. 
The natural limitation is dictated by the availability or uniqueness of certain materials, usually precious stones that does not allow big volumes. Extreme labor and skill requirements can also be viewed as natural limitation. On the other hand, intended limitation is catering for customers prepared to pay higher price for their jewelry, in order to preserve its uniqueness. The intended limited editions are usually accompanied by certificate stating the total number of manufactured pieces, as well as the manufacturing process (handmade. cast assisted etc.) A number stamp on the piece, states the consecutive number opposed to the total number manufactured. For example 3/10 indicates that this is the third piece out of ten possible. What number constitutes limited edition is arguable. My opinion is; it should not be more than a dozen.