I need to find out how much a mexican coin is worth?

the markings on the coin are as follows. (on the left of the heads side bottom to top) Juarez 1987 $ 50 then looks like 5 stars. Just to the right of that is the likeness of Juarez.To the right of that is what I think is a mint mark of a O over a M. The other side has Estados Unidos Mexicanos around the edge then a bird holding a snake in its mouth and one claw,its other claw is holding something I cant make out. Thank you for your time & patience Johnny