Hello,
I was searching the Internet for some unrelated information and ran into an excellent article from 'Wexler's Die Varieties'.
This particular page explains with some photographs the process of how a re-punched mint mark evolves.
Also, I never knew that the following mint marks even existed:
1) C for Charlotte (gold coins only) &
2) D for Dahlonega (gold coins only)
I just thought it might be of interest to any interested party:
http://doubleddie.com/58243.htmlmdpmedia