Cheapest priced copy (Core Set 2020): $0.35 at Card Kingdom, near mint, their price list as of .
Diviner's Lockbox 
Artifact · Uncommon · Core Set 2020 · #225
{1}, {T}: Choose a card name, then reveal the top card of your library. If that card has the chosen name, sacrifice this artifact and draw three cards. Activate only as a sorcery.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Core Set 2020 | 225 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 12 July 2019If the top card of your library does have the chosen name, it will be among the three cards you draw.
- 12 July 2019If the top card of your library doesn’t have the chosen name, it remains on top of your library. Perhaps, if you find the right key, you can untap Diviner’s Lockbox to try again while you know that card.