Price to follow
Quite sure this is a French divers knife used by the special forces too.
To one side of the handle where it meets the blade is has 'STAINLESS' and the other side 'MADE IN FRANCE. INOX'
 
One of the eldest brand in diving. Founded by Georges Beuchat who had first started to sell free diving gear and underwater housing under the name of Tarzan. After a law suit with MGM for using the name "Tarzan", the manufacturer changed its name to Espadon Tarzan, then Espadon and Beuchat.
 
The writing is very worn but from research  I can see this is what it says.
Serrated to one side.
29cm long