You can get the GM chat, stating they box.

You can a screenshot/video of a boxer.
But there's no way of knowing which boxers are also GM's.

I'm quite sure, some of our dual-boxing members also happen to be GM's.
This is a large site, with a ton of membership and the best boxing information for warcraft.
However, we will not be able to tell who is a GM and who is not.

They are prohibited from playing on the same server that they GM on.
And are not allowed to mention they are a GM, while on their own toons.