Dear Mr. Belton,
Thank you for posting your inquiry on History Hub.
Official Personnel Folders covering the period 1850-1951 are held at the National Archives at St. Louis. According to information on their website, they do have records from the Department of Treasury in these holdings. The listing on their website indicates these folders begin for Treasury in 1883. However, you may inquire with them to see if Mr. Barboza has a file. Information on these files and their contact information can be found here: https://www.archives.gov/st-louis/opf
The vast majority of RG 56 (Treasury Department) records are held at The National Archives at College Park. According to the Guide to Federal Records, it appears there are some personnel related records among their holdings. https://www.archives.gov/research/guide-fed-records/groups/056.html#56.3.2 You may contact them via this email: email@example.com
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.
Thank you kindly for your response and advice about who to contact. I've since contacted the St Louis and College Park archives and will wait to see what they say.
I'll add that Antero Jose Barboza also worked as a Post Office clerk in New York between 1877-1880. He was employed by the United States Post Office Department and not the Postmaster. Do you know if the Post Office Department kept detailed records of its employees? If not, is there anywhere else you recommend I can look?
Thank you again.
The Official Personnel Folders in the custody of The National Archives at St. Louis would be the primary place to check if Mr. Barboza has a federal personnel file.