Can you help identify this item please for a fellow collector

Can anyone identify this unknown A/P training mine ?
there are no markings on it and cannot find a way to fit a safety pin, through the arming ? mechanism protruding from the side , any help in identifying this would be much appreciated by myself and the collector who owns the other one, bought at the War and Peace show in 2012.















































German ? Diameter is 4.5 inches by 2.5 inches high Any ideas please