This primary source comes from the Records of Naval Districts and Shore Establishments.
National Archives Identifier:
7450327Full Citation: Twin Launching of USS Threadfin (SS 410) and USS Piper (SS 409) at Navy Yard, Portsmouth, NH ; 6/26/1944; Records of Naval Districts and Shore Establishments, Record Group 181. [Online Version, https://www.docsteach.org/documents/document/twin-launching-of-uss-threadfin-ss-410-and-uss-piper-ss-409-at-navy-yard-portsmouth-nh, April 20, 2024]