Starting back in October 2010, I had (what turned out to be) three generations of plastic prototypes prepared. With each generation things improved. Such as proportionality and position of the lug rings and comfort on the wrist. Below are shots of each generation and finally a shot of the prototype steel cases (which are awaiting some minor tweaks before full case production starts).
Note that the lug rings were as thin as possible and had "tabs" which descended to provide spring bar attachment points. The lug rings were also on the same plane as the main case body. This design did not conform to the wrist as well as I would have liked. Also, the main case body had a minimal amount of space above the dial for the hands.
In this second generation case, note how the main case body is taller and the lug rings are lower in relation to it.With the lug rings lower, the overall case now provides a center contact point on the wrist which is recessed/contoured in relation to the lug rings. This makes the case more conformal to the wrist. Also, notice how the lug rings now taper and blend more smoothly to where the lug rings meet the main case body.
With the third generation, the lug rings are now angled downward from the main case body. This provides a more harmonious appearance and again increases comfort on the wrist. The lug rings are now essentially a constant height from the spring bar attachment points to where the lug rings blend into the main case body. The case (both the main body and the lug rings) are "barreled". Meaning they have a slight outward bulge or contour. This makes the case look more substantial and pleasing to the eye. And it only added a couple of tenths of a millimeter to the case width.
Current stainless steel prototypes