Posted By:
fkwAnyone who says they have never tried to erase a small pencil mark on the back, is lying 
The way I look at it, you may want to try to erase it. But if it is stuborn and doesnt seem to erase easily, then give up and leave it alone. Some old pencil doesnt erase too easily and you may end up messing the surface up with all that rubbing.
That pencil mark on the back of 90% of the 1921 Herpolsheimer cards doesnt come off like you think it might