An envelope for use in containing and authenticating a ballot is presented. The envelope has a containment region dimensioned to receive a ballot or other desired document in accordance with the particular application with which the envelope is used and has a pre-defined area on the back to carry the signature of a person such as a voter using the envelope to vote by mail. A flap portion outside the pre-defined area is used to seal the containment region. A window cover is substantially in registration with the pre-defined signature area to obscure the signature in a first operative configuration and to reveal the pre-defined signature area in a second operative and to re-obscure the signature area after the signature area has been revealed whereby the ballot remains sealed during the pre-defined signature area obscured, revealed and re-obscured configurations. The window cover is arranged for automatic removal by mechanical opening means for automated processing.