U.S.currency is printed in 3 stages.The first being the back,it is allowed to dry.Then the front,same thing.Last but not least the last printing is the serial numbers and the treasury shield that are printed in an overprint press.Yours looks like it got offset in the last printing(ie-serial numbers and tresury shield).Definitely worth more than face value.How much? Who knows? I think i'd hold on to it for a while.It's not going to lose any value,being an error note and all.BTW-it doesn't look fake to me.I can clearly see a few of the security features on your bill.The watermarks and the strip are both visible.Be wary of dealers,ask what they would sell it for if it were thiers to sell.just because they deal doesn't mean they're word is gold.Definitely DO NOT SELL TO A DEALER!!!!