A container includes a casing having an opening and a first abutting edge surrounding the opening. A cover is selectively mounted onto the casing for closing the opening, wherein the cover has a second abutting edge laterally extending therefrom and abutting against the first abutting edge when the cover closes the opening. A puller extends from the second abutting edge of the cover. A snapping device is formed between the casing and the puller. The snapping device includes a plug formed on the puller and a socket defined in the casing for temporarily receiving the plug and holding the plug in place. A weakened portion is formed on at least one place of the puller such that the puller is irreversibly curved after being lifted due to the weakened portion and the curved puller is used as a basis for easily identifying whether the container is illegally operated or not.