Cash Box was a US based weekly magazine for the music industry trade publishing record charts. This two page advert was to support sales during the stadium tour with Traffic and Free.
The text is clearly written for shop owners.
Part of the campaign was also a special promo album, 'An Island Sampler', with ten sample tracks of the artists mentioned. It has two catalogue numbers, one for each side: SPRO-6619 and SPRO-6620.