Hard to tell and as galenrog mentioned the multiple hits on the back would lead me to believe that the mintmark was the recipient of a hit, etc. When zooming in on the picture it blurs to the point where I can't distinguish if you have an RPM or not. If it is an RPM, the condition of the coin unfortunately would diminish any additional value that the RPM would have provided in my opinion. I would just add it to the return pile. Interesting find though.
One of the things I did, years ago, to help identify errors, including repunched mint marks, was to print high resolution images of several examples of different errors. I still use the several binders of images today. From time to time I still add images. It helped me learn more about, and identify errors of all types. A similar system could help you, should you be serious about errors.