The 1878 Twenty Cent Piece is a proof-only issue in this extremely short series that is highly desired by collectors. It has the second lowest mintage in the series at just 600. The date is scarce from the circulated grades all the way through PR66. The value escalates at a gradual pace up until the finest known grade of PR67, which is rare. The auction record for this date is a CAC approved NGC graded PR65, which brought $24,725 at a Stack's Bowers auction in 2011. As cameo and deep cameo pieces go there is an expected, yet subtle, premium. Only 133 have a Cameo designation from PCGS and NGC and only 5 exist in Deep Cameo. Deep Cameos are very rare across all Twenty Cent dates.
| coinage-type | Seated Liberty twenty cent piece |
| desg | PR |
| designer | William Barber |
| diameter | 22 |
| edge | Plain |
| fineness | 0.9 |
| material | 90% silver; 10% copper |
| mintage | 600 |
| ngc-id | 27H5 |
| obverse-description | Lady Liberty is seated on a rock, holding a staff, and bearing a shield with the word LIBERTY on a flowing ribbon. 13 stars have adorn the periphery and the date appears at the bottom center. |
| pcgs-link | 5306 |
| pcgs-number | 5306 |
| prefix | Proof Only |
| reverse-description | An eagle is prominently featured with the words UNITED STATES OF AMERICA * TWENTY CENTS around the periphery. |
| weight-grams | 5 |
| year-display | 1875-1878 |