Peraion Graufalke
First Post
According to your rule, Iron Armbands of Power should be Common.
You can test the validity of your hypothesis by verifying if they actually are.
Cheers, -- N
First off, it's not my rule; I didn't write that article.
Second, the Gauntlets of Blood are also an exception to this rule. (Or should we call it a guideline?

Third, maybe they realized that Iron Armbands of Power are simply too powerful to be Common, which they are IMO.
YMMV.