Stormrunner
Explorer
Actually, coating the back of a piece of glass with a thin layer of metal in such a way that the metal is polished/reflective is a fairly difficult job, requiring some highly toxic chemistry (Alchemy). Glass mirrors are thus a modern item. Medieval mirrors were almost always of polished metal - bronze, steel, or silver. A glass mirror would be a very expensive, masterwork item. Of course, since the item in question is magical it has to be masterwork by default, so it could very well be glass. On the gripping hand, it's also a very expensive item to create, so presumably the creator would want it to be as non-fragile as possible. (Mental image of a block of solid, silver-plated and polished steel, 9'x4'x1', basically a chrome version of the 2001 slab..."The mirror weighs HOW much?")
