Hi. Was just wondering if anyone could help me out. What's this caseback decoration technique called (the small circles), and how is it achieved? Thanks!
Generally speaking that is "engine turning." Accomplished with a small abrasive disc, wire brush, dowel end with abrasives applied, or other means, one at a time, and usually in an overlapping pattern. Not only for watchmaking but also aviation, automobiles, home decor, etc.
Perlage or perlée "Watch components that are given a perlée pattern may include the movement main plate and bridges, the inside of the watch case and the watch-case bottom. The perlée patterned parts of a wrist watch are commonly invisible from the outside except if the watch has a transparent casing or deliberately exposed internal parts. Further grinding patterns used by watchmakers include the clavus pattern, also known by the French term oeil-de-perdrix (partridge eye)."