Performance Armour
"Because you don't need to sacrifice your performance for your appearance"
Etching is a process that was utilized extensively on some styles of armour in medieval times.  It is the process of creating shallow grooves in the surface of piece of armour by either carving, abrasion, acid, or electrical current.  These shallow grooves can form patterns that are essentially only limited by the imagination and skill of the craftsperson.

Etching can form extremely complex and detailed patterns, and provides a very high level of up-close visual interest on your armour, while not altering the overall "from a distance" look.

The end-product usually looks something like a two-tone piece of armour, with the surface being highly polished, and the depressions formed by the etching process being more matte. 

Etching is available on Steel, Stainless Steel, and Titanium armours.

Etching is a completely custom process, and will be quoted on a case by case basis, based on the complexity of the desired design.
Etching
This is an etching example of a Brass plate that will be cut to size, and used as trim on the center of a simple breastplate.  This celtic knotwork design was supplied by the customer, and has been etched into the brass at this point.  As a point of reference, this entire etching measures 3.5" x 3.5" square, and most of the etched lines are less than 1 mm in thickness.
This is an example of a Jerusalem Cross Etched into the side of a performance bascinet.  Note that just normal etching will achieve this sort of "frosted" look, while being fully as durable as the material that it is etched into (in this case 12 guage stainless steel).  The design will not rub or scratch off over time, it is part of the underlying metal.
These are further examples of etching.  Above, spaulders etched with a household symbol and the wearer's name in runic.  To the left a trelliswork pattern on a helm.  and below a Griffin etched onto a titanium vambrace and inlaid with 18k gold (incredible detail on this one, the entire etch is approximately 3"x4", click the picture for a blowup)