I don't know a thing about cured ham, but I just opened this ham, and while I realize a cured ham probably has a peculiar smell, I can't imagine this horrific stench being intended. My entire apartment smells like a trashcan on a hot day, and the ham has both black and green spots on it. Seven meters away, the smell is still strong enough that it just about makes me gag, and every instinct I have is telling me this is not edible.
tl;dr: are jamon serrano hams supposed to smell overpoweringly like old mouldy food, or did I just blow $80 and a perfectly good towel on a worthless chunk of rot?
Follow-up: I've been in contact with the store, and I'm going to go get a refund. I showed the ham to some knowledgeable people in real life as well, and they agreed that it's spoiled. Thanks a huge lot for all your helpful answers!