Sorry for the delayed reply Mr Gus, I have been away and didn't have the password with me to log in. The main crater is about an inch across. I haven't found anything on the ground nearby but it is grassed and I haven't tried digging it up. These are the replacements for the panels which were pinched a while back. It could conceivably be malicious when the perps came back and found the new security measures. But perhaps I'm getting paranoid.