Invention of the Virobloc
At first, the Opinel knife had four components: the blade, the handle, the shell ring and the rivet. The shell ring was needed to firmly rivet the blade to the handle.
In 1955, Marcel Opinel, wanting to improve the safety of the knife, invented the Virobloc® system. He added a rotating lock which slides on the shell ring, closing the groove and therefore locking the blade in its open position. This is a simple idea but with a complex implementation.
In the 90s, the Virobloc® system was modified to allow the blade to be locked in its closed position. At first, it was only used on a few references, but by the year 2000, it was added to every Opinel knife.