That particular emblem has been in use on US Marine Corps buttons ever since 1821, continuing even to the present day. I cannot be absolutely certain from looking at your photos, but because your US Marine Corps button APPEARS to have a "low-convex" (low/nearly flat) front, it was manufactured sometime in the 20th-century. The 19th-century ones had a distinctly higher "dome" shape, and the "raised border" around the eagle was less high-raised than on your button.
I appreciate your saying you respect my opinion, because I try very hard to be worthy of the respect I receive from good people like you. But to give you some additional assurance that the ID and dating I gave you is indeed correct, here's an old (2008) discussion here on TreasureNet. Note that the button's face is low-convex, and its rim is high-raised in relation to the rest of the button's face. http://www.treasurenet.com/forums/t...ne-button-update-more-likely-post-1902-a.html