U.S. National Archives (Record Group 104, Entry 229, Letters Received 1873-1932) Public Deposited
The corresponding National Archives (NARA) online catalog entry is https://catalog.archives.gov/id/7065060. The material scanned here does not comprise the entire NARA entry.
See also the National Archives & Records Administration numismatic finding aids at https://nnp.wustl.edu/library/archivedetail/538870.