Golf ball 2 has a center 4, a mid layer 6, a reinforcing layer 8 and a cover 10. The method of evaluating a film includes acquiring, with respect to a specimen including a plurality of films stacked on each other, ion dose-dependence data of intensity of \u03b3-beam generated by hydrogen resonant nuclear reaction, and fitting the data with a functional equation of the ion dose. 5 parts by weight of carbon black or graphite. A radiation sensitive marking material such as titanium dioxide, for example, can be provided in both the article and a markingly associated window of packaging material.