While the damage reductions are rather unappealing at first, the Iron Parma is one of the most stable small shields available in the game. Contrary to the description, this shield has a lot of potential that is often overlooked by a similar, but medium-sized, shield.
When fully-reinforced and the shield is two-handed, its stability increases from 58 to 68, on par with a fully-reinforced Old Knight's Shield's. Although it lacks the superb elemental defenses and the 100% physical damage reduction of the latter, this shield is more than half the weight and has 4 times the durability, while also possessing decent reductions against fire, lightning, and Dark damage.
Its main weaknesses are the low reductions from magical damage and the auxiliary effects, as well as having a rather high strength requirement for a shield of its class.