~~~ that are reground with original denominations untouched sell for €300-€500+ in the street....

The remnants of previous carving is somewhat not common and fetch even higher prices... see the reverse of the 100 which is minimal to other defined carvings such as the Briotet/Caro resurfaced plaques found years ago.

I hope those 3 examples make it to ChipGuide, legally...otherwise, maybe a written description.