The 1866 Proof Three Cent Nickel comes from a low mintage of just 725 coins with most pieces surviving. Common up to the gem level in which PR65 and PR66 are scarce and PR67 is rare with just a handful existing. Attractive color and strong strikes can be located with some effort. Cameos bring a minor, gradual premium with the increase in rarity and desirability coming from the deep cameos.
| Country | United States of America |
| Year | 1866 |
| Serie | 3-Cent Nickels |
| Denomination | 3cN |
| Mint | Philadelphia |
| coinage-type | Three cent nickel |
| desg | PR |
| designer | James B. Longacre |
| diameter | 17.9 |
| edge | Plain |
| material | 75% copper; 25% nickel |
| mintage | 725 |
| ngc-id | 275L |
| obverse-description | A Romanesque Liberty is portrayed facing left with LIBERTY emblazoned on her crown. UNITED STATES OF AMERICA appears on the periphery with the date at the bottom. |
| pcgs-link | 3762 |
| pcgs-number | 3762 |
| reverse-description | The roman numeral III is centered in the design surrounded by a large wreath tied with a bow at the bottom. This design is one of few American coins without wording on one of the sides. |
| weight-grams | 1.94 |
| year-display | 1865-1889 |