Common look for the "S" of the late 60's. You'll see a mixed bag of variations for this mint mark. From clear and precise to mostly filled in. There are RPM's for these years, but this doesn't look to be one, at least from the picture provided. If you could zoom in on the MM as well, that would help.
I vote 7, but that's just me. Welcome to CT Melody. It's difficult to tell from your photo, even when I blow it up, but it could be a small die chip, which is fairly common.
Our fellow enthusiasts are correct. And if you give us a focused shot of the mm, we may be able to let you know if you have an RPM. I vote 7 as well. It made me chuckle as it reminded me of a response I once gave to a question ("7!"). It's a location joke though; you had to be there.
I voted the other 7 to keep things even. lol Probably a small die chip which is common. Welcome to CT.
