A seal for utility meters and the like has a generally hollow pendular transparent body with two openings spaced along its upper surface connecting with a central cavity. An opaque plastic locking member is inserted into the cavity and permanently connected to the body. For locking the seal irreversibly, a generally U-shaped fastening shackle, each end of which is reversibly bent to form a tang, is inserted through the openings in the upper surface of the body down into the cavity and into locking engagement with the body and the locking member. Frangible fingers and leaves formed in the locking member are designed to provide visual evidence of any attempt to tamper with the seal whether successful or not.