Leather Cuirass Lorica Musculata, I used to think no way but

[Dan Howard]

That is the accepted form of armour in the 15th and later centuries when plate armour was more fully developed. During the 14th century we have no idea whether early forms of plate armour were worn over a complete mail hauberk or whether it took the same form as later plate defences. We are pretty sure that early forms of armoured surcoats and coat-of-plates were worn over complete mail hauberks. We don't know when the hauberk disappeared to be replaced by an arming doublet with mail gussets/voiders.