I've noticed that the concentric circle details on subdials seems to vary considerably on Speedmasters. Some have very pronounced circles (IMO a nice detail) while on others the circles are not--or barely--discernable. Do all subdials have concentric circles? (I read on another forum that this may simply be a part of the dial milling process.) Robert-Jan Broer mentions this here: http://speedmaster101.com/blog/concentric-circles-on-subdials/ but I haven't found a thread in this forum on this topic. Will someone please educate me on what concentric ring details are correct for each reference?