Fossil-like disc-shaped stone

Fossil-like disc-shaped stone

Observation - Fossil-like disc-shaped stone - UK and Ireland. Description: This has been in the family's possession for 60 years+ and came from a London house (near Putney Heath), where it was left by the previous occupant. Nobody can tell me what it is: is it a fossil, artificial or what? My guess is that it is one of those odd

This has been in the family's possession for 60 years+ and came from a London house (near Putney Heath), where it was left by the previous occupant. Nobody can tell me what it is: is it a fossil, artificial or what? My guess is that it is one of those odd fossils occasionally found in London Clay.

It os approx 25cm diam - have included shoes in photo for scale! The apparent structure on the disc face is also visible on the reverse side.