This is a restrike, made in the 1860 or 1870s, using the obverse design originally used on J93-J94/P105-P106 combined with the reverse die, with 'Medium Letters', which was also used with other 1838 and 1839 obverses to produce coins for sale to collectors. Both dies shows areas of die rust.
It was attributed to Gobrecht in the original editions of Judd but a July 12, 1843 letter from W.E. Dubois to Matthew Stickney in the Peabody Essex Museum attributes this design to Kneass as noted below.
"One half dollar of 1839, of a die which you never saw before, nor did I, until today. This die was made by Mr. Kneass, the late engraver, since deceased. A very few pieces were struck; I don't think I could get another, except for the Cabinet, where there is none as yet".
Stewart Witham noted 152 reeds on these, which according to a reed count listing from Bill Bugert of the Liberty Seated Collectors Club, means they were likely struck some time between 1861 & 1871.
Only 2 are known in silver as follows:
1) Frossard, Garrett-JHU, Bowers and Ruddy 11/79 Garrett I, Auction 81, Bass-HWBRF, Bowers and Merena 5/99 as PCGS64, Bowers and Merena 5/04 as NGC66, Southern collection, Simpson collection - PCGS66, illustrated above courtesy of PCGS
2) 64 ANA, 95 ANA - PCGS65
There are also 3 known in copper of J96/P104 as follows:
1) Witham-Auction 81, Queller-Heritage 1/09 as NGC66BN, Simpson collection - PCGS66BN
2) Mitchelson, Connecticut State Library, gem proof
3) Weaver, Bass-HWBRF, Bowers and Merena 5/99, R. Shippee - PCGS64BN