The problem is that I very highly doubt that we can actually forge custom designed equipment, even though some, perhaps in wishful thinking, seem to have taken forging to mean that. Much more likely, forging behaves like in other games with similar mechanics, which is that if you have the appropriate materials, you can take them to a forge, and used them to create items from a generic list of premade items, these could just be default items, or maybe some items on that list can only be acquired by forging, you might be able to craft any item on the list if you have enough skill, or perhaps you need to learn how to craft certain items first, at the very least, I think that would be logical for more exotic items. But either way, I doubt we can actually design our custom weapons and armor when forging. Now, in theory, it would be nice to be able to do that, provided the system gave us enough freedom to not have every custom made sword come out looking like the same one with a different colored blade or a slightly different handle, but I find it rather unrealistic to actually expect that from the game. So it doesn't really explain the sword, more likely, the sword is just one of the default weapons, maybe it's glass, maybe it's elven, it may even be some other material we haven't thought of, possibly because it's new to the series, but I doubt it was custom designed in the game.
You realise it could simply be Elven made glass equipment...
Well, that could technically be the case, as maybe glass is made by elves, but then that renders the debate irrelevent as I'm assuming there's only one kind of equipment called glass and one kind called elven in Skyrim, much like in Oblivion. When we talk about elven, we're specifically refering to the style of armor and weapons called "elven" (I don't want to say material as I doubt elven armor is actually made of a material called "elven".) not armor and weapons made by elves in general, and when we speak of glass, we mean armor and weapons made of glass, whether these are made by elves or not is irrelevent.