Question for the Physics-Minded

Recently I bought a new can of coffee.

I removed its plastic lid, and admired the shiny foil seal. On one side, ordinary atmospheric pressure. On the other, "vacuum." Its rim is attached to the circular rim of the can. The forces on it balance into a smooth convex form.


I began to wonder:

What shape is this?

Paraboloid? Section of a sphere?

I'm thinking it's a catenary of rotation. Am I right?