@Stinley It’s interesting that you thought they meant “is it still the top (i.e. the lid which is called the top)?” I was pretty sure they all thought that was what you were asking already.
I agree with the others – it’s a lid for a jar and the side called the top of the lid is still the top of the lid when it is lying upside down.
However it is also a valid taxonomical philosophical question, as topness is not an absolute fact, but a question of interpretation. Linguistically and how people use it, ya almost everyone is gonna say the top of the lid is the top of the lid no matter which way you turn it. However, the only fact that is absolutely true it that it’s a piece of stuff shaped like that, and you might know it was originally a lid. However if you decide to use or interpret it as something else, another part could be the top in that interpretation of the object. For example, if you decide it’s a sign or radar dish or cat food dish and use it that way, the top might be another part in those contexts/uses.