Right, that's normally what I'd use in this situation. But that means something more like "approximately equal to", whereas this notation seems more akin to "eq

Right, that's normally what I'd use in this situation. But that means something more like "approximately equal to", whereas this notation seems more akin to "equivalence" as in an equivalence class. I don't have a clear memory of what notation we used for that in school, but it wasn't this symbol.