Found this today one side is completely not there and the reverse is the regular usual nickel. Is this a big error or pmd
It was simply ground down, and sorry, it is not an error. Just someone with too much time on their hands. These pop up here quite often. Someone, maybe, who is trying to confuse a new collector.
It's alright... no harm done. Tommy already did a fine job in answering your question, but I would most respectfully caution against assuming this is the result of wish to fool new collectors. It certainly could be (nothing surprises me anymore) but is just as if not more likely the result of boredom, screwing around, etc with no intent to deceive.
You don't need to apologize! It's just that we see coins like this quite regularly, and it's appalling to see that there are so many people who have nothing better to do with their lives. Chris