Toned 1948 MO 5 PESOS Mexico Question
I saw this coin in an upcoming auction, and I am a sucker for toners. However, this one feels a little weird to me (I'm also not 100% familiar with Mexican coinage). The obverse is toned like crazy, and the reverse is pristine-white. Is that odd for these coins?
Also, how much is "too much" to pay for this coin? It's in an NNC Holder, so I'm not trusting the grade of MS67 that's on it at all. Any help is appreciated.