This is supposed to be an incomplete obverse half dime die trial, in white metal, of Longacre's French head design from 1859 showing just the portrait. As described, in Judd editions 1-7 and Pollock, we believe this piece does not exist and that it is actually a misdescription of the copper dime splasher JA1859-1/P3206.
For the first 5 editions of Judd, this piece was described as a half dime in white metal. When the 6th edition was edited, an attempt was made to add information from Don Taxay's "1976 Catalog & Encyclopedia of US Coins" where the piece was listed as EP271 and correctly described as copper, but, instead of correcting the original entry in Judd, a second entry for this piece was added. Pollock then using Judd as a guide for his book also created 2 items for this, P3203 for the original incorrect entry and P3206 which is the correct one from Taxay and the correct attribution.
Even worse, this piece was described as a dime trial in New Netherlands 4/51 sale and as a half dime trial in the 1958 ANA. The circumference around the portrait appears to be half dime sized in both the 58 ANA sale and Taxay photographs but, perhaps the truth will never be known.
Photo is a scan from the 58 ANA sale.