Superior version of Resist Magic enchantment

Just found something interesting whilst playing and thought you guys might be interested. Those with only vague knowledge of enchantments read the first paragraph, otherwise skip to the bold.

As most of you will know there is an enchantment Resist Magic which is lifesaving against the more powerful mage mobs (and those excessively annoying soul gem turrets...). This enchantment 'caps' (... Yes, I am aware that enchantment magnitudes are technically not capped at 100 Enchantment) at your highest enchantment level and with 5/5 in the Enchanter perk to give a 20% magnitude enchantment. With three wearable items that fit with Resist Magic (Amulet, Ring, Shield), you can easily bring your Resist Magic to 60%.

However, there appears to exist a different Resist Magic Enchantment giving a higher magnitude of resistance. There is a unique shield obtained from the quest in which you retrieve Potema's remains from her Catacombs in Solitude with the enchantments 30% Resist Magic and 35% more damage blocked by shield. Disenchanting this shield gives a new enchantment that is named the same as the ordinary Resist Magic, but 'caps' at 25% Resist Magic rather than the previous 20%. Both enchantments exist in your list, and I would expect that both can be applied to a single item with the Double Enchantment perk, but I have not been able to test it because I'm not quite at 100 Enchanting yet.

I am unaware of whether there are alternate leveled versions of this shield, and if so whether or not this 'superior' Resist Magic enchantment can only be gained from this version of the shield (I obtained it at level 47). Would anyone like to test/confirm this?