Hollow Treasure

Today while hunting a property with a home built in 1960s I had a major signal adjacent to the corner of the home. My Tesoro was literally screaming at me with every passing of the coil. After some initial digging with the Lesche and a confirmation with my pin pointer I found a large twisted hunk of metal nearly 7" down. 

I initially was concerned it may be some weird pipe somehow connected to the house. After further excavation I ruled out that worry as what slowly appeared was a massive block of stone and concrete with a metal insert.

Curious I continued to unearth what appeared to be catapult shot from the siege of Minas Tirith. After nearly an hour of excavation almost 2' down I was finally able to rock it loose. Then with the help of a rope I was able to pull this monstrosity from its earthen home. I still have no idea what this is exactly but my guesses are a makeshift anchor point for a flag, clothesline or fence?

After some cleaning I noticed that worms would wriggle out of small gaps in the side so I examined the core with a flashlight. The cavity appears to be only filled with old soil and of course denizens of the deep. This was an interesting way to start the dirt fishing season for sure. If anyone has an idea of what this may be please help me identify it – but for now it will just be my hollow treasure!