Designed to equip the Royal Navy's "27-knot" destroyers, it also equipped several armed trawlers and served as coastal artillery.
It was then purchased and produced under the name of 76.2 mm/40 Type 41 gun by Japan, which made it the standard secondary armament of its ships between 1890 and 1920. Italy bought and produced them under license by Ansaldo; they were used for anti-aircraft defence during the Second World War.
http://www.navweaps.com/Weapons/WNBR_3-40_mk1.php
QF 12 pounder 12 cwt naval gun (serial #11107), CPP 1943. The QF 12 pounder 12 cwt was a 3-inch (76 mm) multipurpose naval gun introduced in 1894 and used until the mid-20th century. It was produced by Armstrong Whitworth, Elswick in England for use on warships, and exported to Allied countries.
In British service, "12 pounder" was a round reference to the weight of the projectile and "12 cwt" referred to the weight of the gun and breech: 12 quintals = 12 X 112 pounds = 1,344 pounds, to differentiate it from other 12 pound guns.
I have done some research and found my match.
This book from the John Lambert collection ( the same as for the armed trawlers) contains all the necessary information and drawings.
I also made a harvest of other photos always useful for the 3D drawing:
