This only applies to color CRTs that use a shadow mask or aperture grille. Monochrome CRTs, and the few color CRTs that don't rely on a piece of metal to ensure

This only applies to color CRTs that use a shadow mask or aperture grille. Monochrome CRTs, and the few color CRTs that don't rely on a piece of metal to ensure the electrons hit only the correct phosphors, are completely immune to lasting damage from a magnet (although in theory a strong enough magnet could alter the magnetism of the existing magnets that correct the set's deflection). A magnet will still distort the image of a monochrome set, but once you remove the magnet, the image should return back to normal.