Blank and paperboard envelope formed therefrom

A blank for forming a paperboard envelope, the blank comprising:

• a single rectangular sheet of paperboard, having opposed top and bottom edges, opposed left and right edges, and a first surface and a second opposing surface,
• the sheet having a midline spaced equally from the left and right edges, the midline comprising a cut that extends from the top edge to a point spaced from the top edge and a fold line that extends from the point to the bottom edge, and
• the sheet having a first zone on the first surface that extends from the midline to the right edge along the bottom edge, a second zone on the first surface that extends from the bottom edge to a line spaced from the top edge, the line parallel to the top and bottom edges and disposed through the point, along the right edge, a third zone on the first surface that extends from the midline to the left edge along the bottom edge, and a fourth zone on the first surface that extends from the bottom edge to the line along the left edge,
• the first and second zones being configured to join the third and fourth zones, respectively, on the first surface with the blank folded about the fold line,
• wherein, in an assembled state, the top edges form a closable opening with the first and second zones joined to and facing the third and fourth zones, respectively, and the blank folded about the fold line,
• wherein the closable opening has a closed state with the first surface adjacent the top edge between the left edge and the cut and the top edge and the line completely joined and secured to and facing the first surface adjacent the top edge between the right edge and the cut and the top edge and the line, and
• wherein a width from the fold line to the left or right edge is less than a length from the top edge to the bottom edge.