​what is this? found buried in my yard. it’s metal and about 8 pounds.

-first photo is when i first got it out of the ground -second photo is a screenshot from a video of it in my hand for size comparison -third photo is after i lightly cleaned it with the water hose

i seen a small part of it at ground level and assumed it was a rock so i started to dig it up and noticed it was shaped weird and i kept digging (for about 30 minutes) and found this! what could it be?