Possible Vietnam War era Seal Team patch

[Tonomachi]

I purchased this patch at an insignia show in Northern California back in the early 1980s.  The seller didn't have any information concerning the patch which as I recall was something like 10 dollars.  It looks unfinished and the facing material feels like silk but it could be nylon.   You have what looks like a hand embroidered Seal on the left edge of an USMC EGA.  The black vertical embroidery in front of the seal could be a sloppy outline of Vietnam.  It measures between 4 to 4 3/8 inches in diameter.  I've never come across another and was wondering if anyone has ever come across anything like this?