Cheapest priced copy (Magic 2015): $0.49 at Card Kingdom, near mint, their price list as of .
Grindclock 
Artifact · Rare · Scars of Mirrodin · #163
{T}: Put a charge counter on this artifact.
{T}: Target player mills X cards, where X is the number of charge counters on this artifact.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Magic 2015 | 217 | Rare | $0.49 | $0.49 |
| Scars of Mirrodin | 163 | Rare | $0.49 | $0.49 |
One ruling from Wizards of the Coast
- 18 July 2014If Grindclock isn’t on the battlefield when its last ability resolves, use the number of charge counters on it when it left the battlefield to determine how many cards to put into the graveyard.