The short answer
Define the real exposure first: sweat, cleaning, rain or immersion. The housing, seals, buttons, camera and acoustic openings then need a test plan for that use.
In more detail
Protection is a system question. Gaskets, housing tolerances, membranes and assembly control all contribute to the result; a seal material on its own does not establish a protection rating.
The required rating and test conditions belong in the product specification. A visual reference or the performance of another model does not confirm suitability for a new environment.