So, I found this "coin". Appears to be 2 oz of silver, and has the proper weight. About 46+ mm in diameter. Has the look / feel / tone of silver. Mirrored proof-like surface. But I can't find a thing about it online, after several weeks of looking. Has anyone seen anything like it before? Thanks in advance!
All modern bullion pieces struck by the Mexican government would have either an Mo mintmark or "casa de moneda" on them. This one has niether, and is thus a privately made bullion round. Much like with American silver bullion pieces, these are designed after previously existing Mexican coin: http://www.liveauctioneers.com/item/7067670