This concretion has a definite sharp edge around the broadest part, almost as though it is two halves stuck together. I am not absolutely sure, but I think it is of the type described as "cone in cone". The only way to be sure would be to break it open, which I am loathe to do. Concretions are fairly common in the Welshpool area, and I have heard stories that they were commonly used as doorstops. When it has been seen by young children they thought it was a dinosaur egg. It was collected many years ago at Dingle farm, Trewern, Nr. Welshpool in central Wales. There is a comprehensive explanation of concretions by Tony Thorp in issue No 1 of the Silurian magazine which can be accessed on this site.