Enlisted Marines did not wear the Eagle, Globe and Anchor on their lapels of the service uniform (Alpha's) until after the battle of Belleau Woods.
The Asst Sec of the Navy, Franklin D Roosevelt (yes the same one) was so impressed with the Marines performance he petioned the Sec of the Navy to decree that from that day forth enlisted Marines would also wear the Eagle, Globe and Anchor on the lapels of the service uniform.
That is all fact. The rest of the story I've heard, and it has been pass on but I have been unable to confirm it.
Supposely, the Marine Corps was immediately faced with a dilema. It needed a boat load of Eagle, Globe and Anchor devices and did not have them on stock. It (the Corps) sent out a contract and had a boat load made. However, the Eagle, Globe and Anchors were slightly different than the ones on stock (no Cuba, rope wasn't detached, slightly smaller). Again in a dilema, the powers that be fixed the problem the only way they knew how.
The Eagle, Globe and Anchors on hand were now officer's devices and the new ones were enlisted devices.
And in my best Paul Harvey voice...
"Now you know the rest of the story."
Semper Fi and "Let's roll!"