1976-D Dime Reverse Error?

Your coin is a " Greaser", slang for a coin that has been Struck Through Grease. The grease originates from maintenance of the stamping press and it only takes a small amount to disrupt the striking of a coin. At times the grease ends up on the die itself, or it may have dripped onto the planchet before being struck. Either way, the hydraulic properties of the grease are strong enough to alter the force of the strike; leaving a weak impression, or none at all. The occurrence is common enough that these types of Mint error are not an incredibly valuable find. I doubt if a Greaser has ever sold for more than ten dollars, and many command no premium at all. They are however, an interesting fact of the minting process, in my opinion.