Cheapest priced copy (The List): $0.49 at Card Kingdom, near mint, their price list as of .
Clockwork Dragon 
Artifact Creature — Dragon · 0/0 · Rare · Mirrodin · #155
Flying
This creature enters with six +1/+1 counters on it.
Whenever this creature attacks or blocks, remove a +1/+1 counter from it at end of combat.
{3}: Put a +1/+1 counter on this creature.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper