“Specialist” as a rating was created at the start of WW2 to to take advantage of draftees’ civilian life skills (source: https://uniform-reference.net/insignia/usn/usn_ww2_enl_specialist.html). “Specialist A” specifically was made in February 1942 for “Athletic Instructors” (source: https://uniform-reference.net/insignia/usn/usn_ww2_enl_specialist.html). It was famously awarded to professional athletes during the war so they could be paid for their service, for example playing exhibition games or managing recreational facilities/clubs, to keep troop morale high (source: https://chevronsanddiamonds.wordpress.com/tag/navy-physical-training-instructor/). Besides profesional athletes, this rating was also awarded to actual physical training instructors whose job was to physically condition fresh recruits (source: https://www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/u/us-navy-interviewers-classification-guide.html#spec).
Specialist A was officially renamed “Physical Training Instructor” in 1944. After WW2, in 1948, Emergency Rating E took over the job for Physical Training Instructor” and the Specialist A designation was re-used for Airship Riggers. Finally, in 1955, it was re-designated for Aircraft Carburetor Mechanic, before being completely retired in 1959 (sources: https://www.usmilitariaforum.com/forums/index.php?/topic/18617-1942-1955-emergency-service-ratings/, https://www.germandaggers.com/Gallery/USNk.php, https://www.instagram.com/p/CX2d4bRLPPr/).
Tags:
“H. N. Welborn, CSP” is listed several times on this index document of company photos printed on September 27, 2006 by the Naval History and Heritage command: https://webcache.googleusercontent.com/search?q=cache:ahop5LW8GxEJ:https://www.yumpu.com/en/document/view/22306306/companyphotos-printed-9-27-2006-naval-history-and-heritage-&cd=3&hl=cs&ct=clnk.
Patches:
“Ruptured Duck” Honorable Discharge Emblem indicates wearer was honorably discharged at the end of WW2 (source: https://www.tracesofwar.com/awards/2199/Honorable-Service-Lapel-Button—Honorable-Discharge-Emblem.htm). 
Reverse of “Ruptured Duck”. 
Bullion insignia.
