I've never even heard of it...and that should tell you something. Congrats on a good find.
Here is a picture of it. NOM 1500 if that means anything to you. I paid 500 pesos for it. They also had a neat 3 tier bottle that had all 3 types: blanco, reposado and anejo. I really like the anejo best, so I just bought a bottle of it.