Some of the refinements are not obvious and some are hidden but the point is every time I make a plane a bit of refinement occurs and after one makes a certain number of planes the end product can gradually evolve into a much different thing. The Stainless Panel Plane pictured below is full pound lighter than the prototype and is visually lighter as well. The configuration of the assembly pins has been revised 4 times in the last couple of years.
Some changes are purely for functional purpose and some are visual. Whereas some of my first planes used tightly spaced threaded pins for assembly, my later planes use a combination of threaded pins, taper pins or in some cases press fit dowel pins. Most of this can't be seen without holding the plane body so that light reflects in such a way as to make these features more visually apparent.
The new lever cap in the Stainless Panel plane derived from a desire to design a different lever cap for the Winter Panel Plane pictured below. It was a natural progression to incorporate an improved design in the Stainless Series of planes as well.
This refinement is part functional improvement but mostly a visual refinement that allows the lines of the plane to flow together in a more harmonious way. In the pictures below you see one my 912-50S planes in Macassar Ebony with the old style lever cap and the one below with Olive Wood and the new style lever cap. I've made both these planes somewhat recently however the Macassar Ebony plane is part of a matched set that began with the older style lever cap. As you compare the two it's obvious that the lever cap in the picture of the Olive Wood plane is more cohesive with the lines of the plane side.
Of course in some cases it's the process that's refined and one just gets much more proficient at performing a given task and that in itself produces an improved result, and then again the end result is most probably a combination of all of these factors.
I've heard it said "when you quit learning, you start dying", I like the keep learning option myself and continuing to learn leads to more refinement.