Curious about purchase

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83 RX-7 Gsl, 2000 Mazda Protege LX, 2011 Mazda3 Sport i
My buddy bought a ms6 a while ago and suddenly the key stopped working so he brought it to mazda where they told him they couldnt fix it for him. I was curious if anyone has any idea what the key fob actually communicates with or if this would even be worth asking to buy for myself?
 
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