This obverse die impression, in copper, for an 1800 half dime is not believed to be a mint product. It might have been made for use in the production of buttons or other tokens. Because of this, it is not assigned a number in the new edition of Judd.
This piece dates back into numismatic antiquity. It was listed as unique in the 1864 McCoy sale. Since that time, a number of others have appeared to the point where at least a half dozen are known.
Photo is a scan from the Bowers and Merena Kosoff sale.