Armoury (STW building)
It doesnt produce units.
The Armoury specialises in the production of superior quality armour. Although it doesn't train any troops itself, its presence in a region improves the armour of all troops produced by other buildings in that region. It also allows the Famous Spear Dojo to produce Naginata and the Famous Horse Dojo to produce Heavy Cavalry.
Samurai nearly always provided their own armour and weaponry. The same, however, was not true of the ashigaru who were drawn from the lower, poorer classes. The importance of providing standardised equipment to their soldiers was realised by the more astute daimyo during the Sengoku period. Apart from the obvious benefits of making sure that their troops were properly equipped, there was an additional benefit in terms of creating an esprit de corps among the ashigaru.
In Shogun: Total War - Gold Edition, an armoury improves the armour values of any units trained at the castle where it is located. An armoury can also be improved to famous or legendary status in larger castles with subsequent armour benefits for units.