Jianwen Tongbao (建文通寶), did this supposed Ming Dynasty cash coin exist?

Greetings y'all,

I recently came across this image:



(Scott Semans - Creative Commons Attribution 3.0 Unported.)

and was wondering if this is a genuine inscription or a later produced fantasy (perhaps a Chinese numismatic charm), I can't find anything about it in David Hartill's Cast Chinese Coins.