Dear Ms. Robitaille,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the series Card Index to the Numerical and Minor Files, 1906-1910 in the General Records of the Department of State (Record Group 59) that contains multiple references to Mexico AND treasury that might be of interest to you. It serves as an index to the series Numerical Files, 8/1906-1910 and to the series Minor Files, 1906-1910 in Record Group 59. These records have been digitized and can be viewed online using the Catalog.
We also located 44 series of consular records related to Mexico in the early 1900s in the Records of the Foreign Service Posts of the United States (Record Group 84) that may contain some relevant information. These records have not been digitized. For access to and information about these and similar records, please contact the National Archives at College Park - Textual Reference (RDT2) at email@example.com.
In addition, we located your original History Hub post if you wish to review the discussion there.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDT2. We apologize for this inconvenience and appreciate your understanding and patience.
If you have not already done so already, you may wish to consult Foreign Relations of the United States (FRUS). This is a Department of State publication of selected documents from the Department’s files and other sources. Besides providing the text of the most important documents on U.S. foreign policy, FRUS also provides a source citation printed either as a header with the document or as a footnote). Those references to file numbers or other records identification are the keys to locating not only the printed documents but other documents on the same subject not selected for publication. Cited "Lot Files" may be difficult to identify among the records in the National Archives using just the Lot number. If you are interested in using any of those records, please RDT2. FRUS volumes are usually available at large universities or public libraries, and in the U.S. Government Depository Libraries.
We hope this information is helpful. Best of luck with your research!