Engine block VIN numbers

Has anyone ever seen a Corvette engine in which the factory made a mistake (or the engine had a problem at the assembly line and was sent to the repair section )in stamping the VIN numbers.I have what i consider to be an original matching engine that appears to have been stamped,then numbers ground off with a hand grinder,and restamped again over the rough ground area.The engine assembly #'s were not touched and are original,only the serial #.At first i thought it was a crude restamp, but closer examination shows that it was stamped using the factory gang matrix,as the numbers are perfect size, totally straight and correct type.In my mind, an amateur wouldn't have acess to original stamps, and a pro would NEVER do such a crude job (grinding them off )as he would deck the block first.The car is totally matching, and dates on all cast parts are perfect and apprear to be all original.
I wondered if anyone has any knowledge of the stamping process in 1970.