The remaining exemplars of Puerto Rican currency have gathered significant value with the years, particularly in the United States. The value of them within the collectors of that country is due to the special nature of the post-1898 issues. Since they were issued under the same Spanish provincial charter, the Bureau of Engraving and Printing classifies them as "territorial" currency, this being the only unit of exchange of this kind that is recognized by the United States Department of the Treasury.