2 mana artifacts that tap for mana are a pretty standard staple. This would be meant to be a color fixing card in a set that doesn't require cycles of color fixers, but still wants a few hanging around (like Prismatic Lens and Terramorphic Expanse in Time Spiral, or Springleaf Drum in Lorwyn). As for power level, I'd say this is on par with the Talismans from Mirrodin, Prismatic Lens, or Mind Stone, and that seems fine. I'd like to see it at Uncommon, I think.
Brass Stones
2
Artifact
Whenever Brass Stones becomes tapped, it deals 1 damage to you.

: Add one mana of any color to your mana pool.
Oh, and I guess it really should be Brass Stone, but I couldn't resist.
Current Wording:
Brass Relic
2
Artifact
Whenever Brass Relic becomes tapped, it deals 1 damage to you.
: Add one mana of any color to your mana pool.