Cheapest priced copy (New Phyrexia): $21.99 at Card Kingdom, near mint, their price list as of .
Unwinding Clock 
Artifact · Rare · The List · #NPH-164
Untap all artifacts you control during each other player's untap step.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
8 printings · $21.99 to $89.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War Retro Artifacts | 61 | Rare | $24.99 | $29.99 |
| The Brothers' War Retro Artifacts | 124 | Rare | $23.99 | $44.99 |
| The Brothers' War Retro Artifacts | 124z | Rare | — | — |
| Commander 2018 | 228 | Rare | $22.99 | — |
| New Phyrexia | 164 | Rare | $21.99 | $89.99 |
| The List | NPH-164 | Rare | $23.99 | — |
| Star Trek Commander | 359 | Rare | — | — |
| Star Trek Commander | 510 | Rare | — | — |
3 rulings from Wizards of the Coast
- 1 June 2011Those artifacts untap at the same time as the active player's permanents. You have no choice about what untaps and can't choose to not untap an artifact you control.
- 1 June 2011Even if you control more than one Unwinding Clock, you'll only untap your artifacts once during each other player's untap step.
- 1 June 2011Some effects, such as the one generated by Rust Tick's ability, state that an artifact doesn't untap during its controller's untap step. These effects won't apply and stop the artifact from untapping during another player's untap step.