Hi Yes i remember a concrete slab and a large metal ring attached in the park/ grassland behind our house in common lane, sheldon, and dad told me it was a mooring ring for a barrage balloon. It is now called the sheldon country park and the rings may have been removed but now.There was a BB site in Perry Common Recreation Ground immediately behind the houses on the corner of Dovedale Road and Witton Lodge Road. Until at least 1954, there were several heavy iron mooring rings concreted into the ground. I left Birmingham in 1965 so I have no idea what has happened to the area. I doubt if they are still there.