A never built destroyer from 1940:
The Nestor Heavy Destroyer Class was designed in late 1940 for replacing the 1920's designed Aegina Class. With twin British Ordnace/EPK guns 120/45 DP (or 4.7" HA), six 2-pdr (one quad, two singles) and four 20mm Oerlikon AA (made under lisence as EPK30AΑ form 1930) she would be a very effective ship, balanced between AA and surface warfare. Except from guns, she had also 40 Thunder I-N rockets (102mm, 12km range, fin stabilized) and five torpedo tubes with MkIX/MkVIII torpedoes. Propulsion would be two METKA M30 steam turbines with four Vasiliades boilers for 36kn max speed. Unfortunately, the situation of Hellenic Kingdom in 1940-1941 was against Nestor Class. However, Thunder I-N rockets did entered service, on Rhodes Class (a variant of Aegina Class).
Several other ships would have the 120/45 DP gun, among them light cruisers, heavy cruisers and a "seaplane carrier/cruiser" (this would be the rival of Miltiades Class, with two British Ordnace/EPK 152/50 guns, twin 120/45 DP, four quad 2-pdr and several 20mm and a large hangar amidships with catapult for three seaplanes SHAF K-4S).
P.S I have in my mind a post war version of Nestor, built 1947-1952, with 120/45 DP guns, Bofors 40/L60 and 20mm. She would have British radars/directors and later received ASROC and upgraded electronics. Served in Black Sea until end of Cold War.