The Barber design struck from a unique obverse die with date low and less finishing in the leaves atop Liberty's head. This obverse was also used on Goloid dollar patterns from 1878-1880.
Only a single example is known ex Maris 6/1886, Garrett-JHU, Garrett I, Bass-HWBRF, B/M 5/99 as PCGS64, Simpson-Heritage 1/21 - PCGS65
A single example was also struck in copper J1525/P1693 from this die as well.
I believe this is die was the first of this type created by William Barber but was rejected. A second obverse die with the date slightly higher in the field and with fine lines extending from the leaves atop Liberty's head was also created and is described in Pollock as P1690-P1691.
To see both obverses side by side, click here.
For addtional information on this and all 1877 half dollars, click here.
Photo courtesy of Saul Teichman.