Traditional. Rectangle. Compare variations by Luis Fernandez, Pajarita magazine (AEP) 30 and Paul Jackson, Origami and Papercraft. Compare flap variation on “Purse,” Gay Merril Gross, New Ideas for Paperfolding.
Rectangle. Loose flap must be glued down to seal. Traditional, possibly French. Postage stamp seals flap. Reference occurs in British Origami Society Magazine 115. Compare variation Michel Grand, ELFA Library.
Rectangle. Flap slotted into aperture. Adapted from a fold attributed to Frances Levangia; reference occurs in British Origami Society Magazine 114 together with alternative folding method and background of creator.
Made from a square sheet of paper. Flap slotted into aperture. Adapted from a fold attributed to Sumiko Momotani (referenced in British Origami Society Magazine, 128) and Y. and S. Momotani, Image and Expression. See also Hawk Envelope. and Bunny Envelope, Yoshihide and Sumiko Momotani, Origami Kawaii, (ELFA library).
Made from a square sheet of paper. Loose flap must be glued down to seal. Adapted from a fold attributed to Hiroshi Kumasaka (from whose initials its name is taken), OKK vol. 4, ’80, Nippon Origami Association magazine (Japanese Origami Society) vol. 2, Japanese publication. Heart shape can be formed on tip of flap thus producing a Valentine envelope. Compare Kumasaka version.