Of course I've googled the heck out of this stuff since returning. The last Mayan settlements on the south coast of Belize were mid classic period - 600 to 950 AD. The Mayan went and stayed inland during the post classic decline.

So, given the size of this perfect blade, and assuming a few things - that it was mid classic and that you could sell it (and assuming the internet isn't full of misinformation, which it is) then there is a thousand bucks right there.

Dealers are trying to sell similar pieces (sans credentials) online for much more.