As per the U.S. NAVY MARKS (AND OTHERS) ON MARINE UNIFORMS, BY: JOHN A. STACY, REVISED: SECOND EDITION, 2014.
“Navy specialty marks and distinguishing marks produced in materials appropriate for Marine Corps uniforms have become a topic of growing interest and considerable speculation. Specialty marks are the central element of Navy petty officers' rating badges and indicate the wearer's job specialty or rating. When worn by a sailor below the rate (grade) of petty officer, 3rd class, these marks are referred to as striker's marks and indicate that the sailor has qualified in the rating and has been designated as "striking for" the rating, i.e. promotion to petty officer, 3rd class in that specialty. Distinguishing marks are worn, in addition to the rating badge for petty officers, to indicate "qualifications additional to those required for their rating, or who are members of a crew that has attained special merit in certain prescribed competitions.”
“Navy marks are normally found in white on navy blue wool, blue on white cotton, khaki, slate gray or naval aviation green materials. Khaki, slate gray and aviation (forestry) green uniforms were worn by officers and chief petty officers. Marks in dark blue or black on aviation green, which are actually officers' and warrant officers' sleeve marks and/or distinguishing marks of chief petty officers, are sometimes included in collections though they are a completely different category of insignia. Striker's marks would not be worn on these uniforms, though chief petty officers would wear the distinguishing marks.”
“The marks on Marine Corps uniform materials, most of which appeared during World War II, are scarlet on forestry green wool, green on khaki cotton, and yellow (gold) on both scarlet and navy-blue wool. The first two combinations cited are easy to explain. Scarlet on forestry green for the winter service uniform and green on khaki for the summer service uniform both fit with the color combinations used for chevrons on the corresponding Marine uniforms. The yellow marks on scarlet and navy-blue backings were apparently both intended for the blue dress uniform and are not so easily explained.”
“Marks in the Marine colors described constitute a category of insignia for which little documentation has been found. Explanations for this group of insignia, with minimal documentation having been found to date, depend largely on anecdotal evidence, memory, reasoning, and conjecture.”
“Two documents and the memories of one Marine veteran address the issue of authorization. A letter dated November 14, 1941 from Gemsco, Inc. to Marine Corps Headquarters cited requests received for four aviation marks and sought specifications if they had been approved (Exhibit A). The response stated simply, "Such insignia is not used in the Marine Corps." (Ex. B). The second document is from Leatherneck magazine, Pacific Edition, June 1944 (Ex. C). In the "Question Box" column, the writer asked, "Is there any authorization for wearing of Navy striker's badges [sic] by Marines...?" The response, "We are unable to find any authorization for this in Uniform Regulations."
“Further evidence of questionable authorization for these marks worn by Marines comes from Marine veteran James Bernard through two separate incidents. While in transit from the Naval Electronics Center, Chicago to Camp Lejeune for Radar School, he visited a military supply store in Washington, D. C. because "I had seen a few patches on Marines [and] we wanted to know about this new uniform piece." At the shop "...there were many [Navy insignia] on display. One in Marine green and red for about any classification that possibly could apply to us Marines. The person we talked to was evasive but did finally say that they were not approved." Marine Bernard goes on to describe the second incident. "Shortly after our arrival at Camp Lejeune we...fell out for inspection. Actually, the formation was held primarily so the C. O. could speak to us about this patch." The presence of a Marine in formation wearing a mark served as an example "...for him to accentuate that these insignia were not part of our uniform and would be dealt with severely."2 These events took place in May 1944 and, along with the pre-war Gemsco inquiry, reinforces the notion that many, if not all, of these insignia were truly unauthorized. We could question why manufacturers would produce insignia for which there was no authorization except that similar examples abound.”
“There are a large variety of marks that make up this category of insignia from World War II and others which are frequently included with this category by collectors but do not really belong. Some insignia often included appear in different color combinations than described above and actually were for Marine uniforms. There are others which do not appear to be of either Navy or Marine Corps origin. For whom and for what use these various insignia were produced, requires a much closer look.”
With the above being said, USMC uniforms from this time period were found to have these striker marks sewn onto the uniforms.