Polarized lenses may be either with only one side of the lens having the polarized film, or the two sides of the lenses can have a polarized film sandwiched between them. These lenses are usually clear or might have some tint, but the tint does not specify the level of polarization that a lens has.
It is important to understand that polarization is not merely a coating like the gradient tints that are applied on sunglass lenses for style and color vision. In fact, polarization is a complete technological process which involves the etching and crafting of tiny vertical lines on the surface of the sunglass lens, which prevent the horizontally reflected light from penetrating and passing through the lens.
The original lens cannot be converted into a polarized lens, as the technique for creating the protective lenses entails a certain specific manufacturing method which cannot be applied like a coat on a lens.