There's this town with two blacksmiths - one, a swordsmaker and the other, a shield maker. The swordsmaker's swords can slice through anything as a rule and the other guy's shields cannot be destroyed. Now they get cut up with each other for some reason and pit their wares against each other. What do you expect happens?
Can I assume that we are operating under the definition that a shield which has been sliced through is "destroyed"?
If the Shield's property of "cannot be destroyed" is clarified as always being able to repair itself, it would still leave open the possibility of the sword slicing through it freely wouldn't it? (almost as if the shield were intangible at any point it was in contact with the sword)