This is an obverse die trial, in copper not white metal as listed in Pollock and Judd, of just the portrait as used on J1631/P1828 in 1879 and J1654/P1854 in 1880.
The only example known was last offered as lot 552 in New Netherlands 4/51 sale where it was described as follows:
"Die strike from Morgan's Goloid Metric design showing bust only struck on extremely thin copper planchet. This design was used for a pattern dollar struck in 1879 as well as for government heroism medals. Rev. uniface except for the words "Metric Dollar" scratched lightly. Unusual, undoubtedly rare."
Photo is a scan from the New Netherlands sale catalog.