They call it an 'off center' error

If it is missing 20% to 60% for modern coins, it is considered an off center error. If it is only slightly off center, it is called a 'broad strike' error. The coins like this which have a readable date and mint mark are more valuable than specimens that do not. Your kind of error coin lists in The Official Red book as having an average buy price of $5.00. But depending on how high it grades, could be worth more. Plus, a coin is only worth the value we place on it, or what others are willing to pay for it. I know that it is a little pricey to get coins slabbed, but if you are collecting for the long haul, it is better to get them protected, so that your coins can be enjoyed for decades to come. Plus, it is easier to sell a certified coin, than it is to sell a raw coin. Either way, I say go for it, and I hope they grade out well for you.