Dwarven smithy (- 1 healthy, +10% hammers, +10% hammers with copper, +10% hammers with iron, +10% hammers with mithril)
vs
Forge (standard) (- 1 healthy, +25% hammers, +1 happy from gold, removes the 'rusted' promotion)
The smithy which replaces the forge has neither the 'Removes rust' nor '+1 Happy from gold' bonuses at the same cost as the normal forge (250 hammers, - 1 health)
This makes the dwarves at a disadvantage (most of the time - unless player has all metal resources) on a building where you would expect them to be assisted.
suggestion
- dwarven smithy adds +1 happy to gold, removes rust, cost 300 (from 250 hammers)