What is this little iron wheel in my pecan tree? A clothesline wheel?

High in my pecan tree is a little iron wheel. I live in an urban area, what could it have been used for? Is it a clothesline wheel? A well pulley? It says "Samuel Ginns Inc, Cambridge, M" on one side and "Guaranteed Rust Free" on the other. If it's a clothesline wheel, when would it have been installed/used?