A type of electronic seal commonly used by the IAEA. The electronic optical sealing system was designed for substitution of VACOSS seals. Like VACOSS seals, the electronic optical sealing system is a reusable, mechanical- locking seal for long-term storage that monitors light pulses through a fiber optic cable. The seal does not prevent opening and closing. Instead, it monitors the fiber optic cable and records any attempt to open, cut, or manipulate the cable. In addition, the electronic optical sealing system seal includes built in provisions to report any attempt to tamper with the seal body. This could be something as simple as trying to drill a hole in the seal body to gain unauthorized access to the seal data or to switch off essential functions. Any attempt to open the seal's case is stored in the seal's memory. The seal timestamps all open and close events and stores them in an event log, which is also capable of storing other information, including operator activities or state of health information.