Thanks HW7 and CD. Pretty sure we have the correct shape, including the 120 degree symmetry, hole and minus the Tango.
As we said, a common shape, hence the comment about the recycling symbol and link with snooker tables! Road signs also spring to mind, especially as carried in car boots for an emergency. Onwards we plod, meanwhile at least the dog had a walk and the F1 to come. Thanks again.