With an archives identifier, how can I find out if the records are online?

Dear Mr. Rose,

Thank you for your question to History Hub!  The records described as National Archives Identifier (NAID 6131397) are not available online. If the records in question had been digitized, the relevant scans would show up in the catalog search as reference in NAID 45646459 (https://catalog.archives.gov/id/45646459).

The file unit “[1943:] BuPers [Bureau of Naval Personnel] Circular Letters [3 Folders]” from the series titled “Restricted General Administrative Files, 1942-1944” in Record Group 313 are in the custody of the Textual Reference Branch at Archives II in College Park, MD (RDT2) as indicated at the bottom of the link you cited.  Please contact RDT2 via email at archives2reference@nara.gov and provide as much information as possible in order for them to assist you further.

Thank you again for your inquiry and best of luck on your research.