Maverick Annual 1961 - paint on art board, 21 x 14 inches - ink/water stain on right

Page of art, used for the frontispiece (and whatever the back equivalent is called) of the Maverick Annual 1961. The artwork features James Garner, Roger Moore and Jack Kelly.

As far as I can tell the art is painted - perhaps with some inks(?) - although I stand to be corrected. It's on large, thick board measuring approx 21 x 14 inches.

Condition-wise it has prominent staining on the right-hand side, either from ink or water. It also has some slightly blunted/creased corners.