Metal inlay work from Performance Armour is a two step process, first we etch the needed design into the completed piece of armour to a depth of .25 mm and then we electroplate a contrasting metal of your choice into the the etched lines until they are even with the surrounding metal. What this creates is a pattern of different-colored metal that appears to be all part of the same surface as the surrounding armour.
(example: a celtic knotwork pattern running around the edge of a pair of stainless steel pauldrons is etched, and then filled in with copper and polished. You end up with a copper celtic knotwork pattern worked into the surface of your armour.)
This is an extremely durable surface treatment for armour, because the (usually softer) metal used for electroplating is protected by being on the same surface level as the surrounding harder metal (Steel or Stainless Steel)
This is a completely custom process, and will be quoted on a case by case basis.