Abstract: A label holder for mail bags or the like comprises two parts, at least one of which is transparent, which can be superimposed with a label placed therebetween. Corresponding ends of the superimposed parts are provided with locking means for closing the holder, the first of the two parts being provided with an upstanding spool and the second of said parts including a cap portion for covering said spool upon closure of the label holder. The cap portion is formed with an orifice through which protrudes an upstanding lug formed on the upper surface of said spool and provided with groove means, at least partially, around its periphery. A string is attached to the part provided with the spool, the string being wrapped around the mail bag or the like, and then around the spool, whereupon the second part with the cap is closed to cover the spool. A plastic seal is then applied around said groove means in said lug so as to prevent the opening of the label holder.