​Metal object resembling the shape and size of a gravestone with numbers “1120” found partially buried in backyard

Found this metal object that eerily resembles a gravestone partially buried in the backyard of a house I just bought. The number “1120” is on the front with no other numbers or text. The house number is about 1000 off from 1120 and seems impossible it would be the year of manufacture. (Ignore the black dots those are drops of sweat that fell while I was looking at it from above)