Abstract: A reusable electronic seal for a trailer includes a structural enclosure configured to attach onto a shackle of a padlock with an electronic module integrated within the to enclosure. A rechargeable battery circuit with a photovoltaic cell is in communication with a battery permitting the battery to be charged by the photovoltaic cell when the voltage is low. The electronic module incorporates a microprocessor, a random number generator and a liquid crystal display which communicates with the random number generator. A shackle engagement switch is configured to engage the padlock shackle, applying a signal to the microprocessor when the padlock has been opened. When the padlock is re-latched the shackle engagement switch triggers the microprocessor to signal the random number generator to transmit a new number to the liquid crystal display.