Another Alley Mystery

What might this be, and what is it doing in the alley behind my house?



Lots of strange things turn up in the alley, and always behind my house.

This is a MAC Power PC, from what . . . 15 years ago? 20 years ago? It weighs a ton. I could barely lift it to get it out of the way of the trash cans. But why would someone leave it behind my house? Is it some sort of message from God -- like "buy Apple stock?" I think it's a little late for that!