Doublet, Arming
Terminology is a little tricky here, while ‘Coat Armor’ is just a vest, the ‘Arming doublet’ is actually a long sleeved coat with some sections of mail embedded to protect weak spots in the armor worn over it. This makes very effective under-armor for plate harness, granting +1 Bypass when worn in conjunction with plate harness (in lieux of a gambeson or aketon). Medium or full armor which incorporates a gambeson can be fitted out with an arming doublet as an alternative for an extra cost, this would confer an additional +1 Bypass (no DR bonus).