Isn’t plate armor made to fit very tightly to the wearer? If Euron stalked the ruins of Valyria looking for some VS armor wouldn’t the chances of it fitting him be so low that we can assume his armor in The Forsaken is a glamour?

It was indeed scale armor:

warsofasoiaf:

Well, Euron’s armor isn’t plate mail. If I remember correctly, it was described as scale armor, and that could mean many things. Unfortunately, Aeron takes one look and has other things on his mind, rather than giving us a description of the exact style of Euron’s new raiment. I’ve always envisioned it in the form of the lorica squamata, but that’s because old Valyria is supposed to have this Roman Empire vibe to it.

Thanks for the question, Anon.

SomethingLikeALawyer, Hand of the King

“Euron Crow’s Eye stood upon the deck of Silence clad in a suit of black-scaled armor like nothing Aeron had ever seen before. Dark as smoke it was, but Euron wore it as easy as if it was the thinnest silk. The scales were edged in red gold that gleamed and shimmered when he moved. Patterns could be seen within the metal. “

And unlike plate armor, scale armor is relatively easy to re-size: because it consists of little scales that are sewn or attached to an underlying garment and then to one another. If you have the time and enough scales, going up or down sizes is simply a matter of removing the scales from the underlying garment, adjusting or replacing the garment, and then replacing the scales – subtracting scales if you’re going down a size and adding them if you’re going up a size.