Real Photo Post Card by Kowalak, River Edge, NJ.
The movie slate on the front reads: Proscenium, Dir. Dick Lester (standing next to John Lenon in the above postcard), Gil Taylor.
The man standing in the far left corner is producer Walter Shenson.
So this must be when they were filming A Hard Day's Night.
A Hard Day's Night, released on July 6,1964, is a British black-and-white comedy film directed by Richard Lester and starring the Beatles—John Lennon, Paul McCartney, George Harrison and Ringo Starr—during the height of Beatlemania. It was written by Alun Owen and originally released by United Artists. The film portrays a couple of days in the lives of the group. Gilbert Taylor did the Cinematography.