Cheapest priced copy (Double Masters): $0.99 at Card Kingdom, near mint, their price list as of .
O-Naginata 
Artifact — Equipment · Uncommon · Saviors of Kamigawa · #157
This Equipment can be attached only to a creature with power 3 or greater.
Equipped creature gets +3/+0 and has trample.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $0.99 to $7.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters | 278 | Uncommon | $0.99 | $1.49 |
| The List | SOK-157 | Uncommon | $1.79 | — |
| Saviors of Kamigawa | 157 | Uncommon | $1.49 | $7.99 |
3 rulings from Wizards of the Coast
- 7 August 2020O-Naginata can become attached to a creature only if that creature's power is 3 or greater before O-Naginata is attached to it.
- 7 August 2020O-Naginata's equip ability can target any creature you control—but if the creature's power is 2 or less, it won't become attached as it resolves.
- 7 August 2020O-Naginata becomes unattached if the equipped creature's power is reduced so that its power is 2 or less, including the +3/+0 from O-Naginata's effect, as state-based actions are checked.