John, Paul, George, Ringo.
In 1964, Topps decided not to "Stick to Sports" and made several sets of The Beatles. There's a black-and-white set, issued in three series, a "Beatles Diary" set, a set featuring the album and movie "A Hard Day's Night", and also a 64-card color set that includes today's "Card of the Day". This is card No. 35 from the color edition, known as "Beatles in Concert". It's a classic shot of the band, making this card a standout.
By '64, Topps had already been experimenting with entertainment-type sets, including "The Beverly Hillbillies" in 1963, and before that a set of "Mars Attacks".
It's not especially valuable, with this card in similar condition to mine being available for only a few dollars.
Here's what the back of the card looks like: 
Mike Schopp
Mike Schopp