Hello Marie, and thanks for your question.
The reason I believe you have not been able to find information about this coin is because it is not a 'coin' at all, with a denomination, as in 'for legal tender'; it is a medal or medallion which was made in 1910 to commemorate the centennial of Mexico's independence won in 1810.
I'm very familiar with what this medal looks like and you can see a picture of the both the front and the back of it, to compare to yours, here (I believe it is your exact one):http://www.ebay.co.uk/itm/SILVER-INDEPENDENCE-MEXICO-MEDALLION-1910-/300613881053
As you can see, this UK ebay auction from Oct. 2011 had a starting bid of 475 British Pounds. This amount converts to $743.43. It's actual value would depend on it's condition and the actual weight of the silver. It's always best to have an experienced appraiser familiar with this type of medal, examine it in person and then give you the most accurate value. The figure above is just a reference point for you. You may also have success in bringing it into a local jeweler who specializes in silver coins/medallions.
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