It's not. The inside loops of the 8 would show the tell tale pick up. The loop openings would have a very flat edge and look very offset from each other. The loop openings on yours are like they should be, centered over each other. Compare to the photo below.
Assuming that there was only one reverse die (which seems to be the case from a quick check at Heritage), your coin is not the 1918/7. Here is the 1918/7 reverse MM.
Thanks @jtlee321, the obverse photo is very helpful. I'm not sure, though, what you have indicated with the reverse mint mark: is it that the OP coin shows a slight tilt to the right and the correct 18/17 shows a slight tilt to the left? Steve
There a few diagnostics for these coins; however most are missing due to wear on your coin. It does look like the bottom hole in the "8" is the correct shape. So I suggest this. Send the coin in to a TPGS ONLY if there is a very slight rotation of the dies. That is one of the diagnostics for these nickels. If this turns out to be genuine, it appears to have a die break over the date and across the braid. I have never seen this on a genuine overdate. While one diagnostic on some of these is a die break into the cheek from the braid, it is higher on the genuine (in a worn area of your coin so no help). PS: If I saw this coin for sale, I would jump on it RAW! EDIT: BUT NOT if being sold as an overdate unless it were certified! Hi Steve!
If you have already obtained the coin, you are stuck with it. If not, is it being sold/listed as a 1918/7?
Welcome to CT...I'm getting ready to buy this one...when I win the lottery! http://www.ebay.com/itm/1918-7-D-BU...001439?hash=item2eecf5679f:g:O1oAAOSwFEFXJV95