Show guard guards secrete secret of letter an american Amerl cau baa has invented an en delope which records ot of itsel any attempt to tamper with its contents the flap Is imbued with come chemical composition which r a a operated upon by a dampening p or any other means of nitrating net rating to its in closure reco the transaction by causing the words attempt to open to appear it Is thought thai that the inquisitive will think twice before pur suing their researches in face of such an invention |