Freddie and the Dreamers were a British pop group who gained fame in the U.S. in the wake of the Beatles. Their song "I'm Telling You Now" hit #1 in the spring of 1965, and Donruss probably rushed out this card set soon thereafter.
The card fronts feature a posed black-and-white photo of the band, surrounded by a white border, while at the bottom are the card number, the set title, and the admonition to 'Collect all 66 cards and place backs together to make a giant autographed photo of Freddie & The Dreamers.' Indeed, the backs were puzzle pieces.
It's difficult to imagine this card set having much value for younger collectors these days, other than as a period piece, but the cards themselves are inexpensive to obtain and they do help provide an idea of the time and mood in which they were released.