[I actually had to google it to be sure, but yes, he was one-armed in his legends too. It was lost in one of the many battles that the Round Table took place in, and Bedivere became accustomed to fighting one-armed after that. The legends most definitely did not mention a magical silver arm, though. That would be the first clue that there was something different about this Bedivere.

One of the pairs of black gloves fit, and Bedivere slipped it on and flexed his fingers a bit. They weren't at risk of ripping, which was good, because Bedivere had definitely ripped cloth before with his silver arm.]

And it wouldn't do to have them see me, yes? At least, not until you have established our working alliance with them.

[Even if his way of describing it was odd and dated, he seemed to understand what Dazai was going for. So with a nod, he went into spirit form again.

Interestingly enough, his armor and clothes seemed to disappear when he did too.]