Cheapest priced copy (The Brothers' War): $0.35 at Card Kingdom, near mint, their price list as of .
Tawnos's Tinkering 
Instant · Common · The Brothers' War · #191
Put two +1/+1 counters on target artifact, creature, or land you control. Untap that permanent. If it isn't a creature, it becomes a 0/0 creature in addition to its other types.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War | 191 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 14 October 2022If an artifact or land that becomes a creature this way has been on the battlefield since the beginning of your upkeep (even if it wasn't a creature at the time), it can attack during your turn and its abilities may be activated.
- 14 October 2022Tawnos's Tinkering doesn't grant haste, so if a noncreature permanent that entered the battlefield since the beginning of your upkeep becomes a creature this way, it can't attack until your next turn. Any activated abilities that it has with a {T} symbol in their cost also can't be activated until your next upkeep step. Notably, this means a land that entered the battlefield after your last upkeep can't be tapped for mana if it becomes a creature this way.