Naval Gun 381/40 here is actually build to equip the battleships of the Francesco Caracciolo class.
But it was scrapped and 7 of them became a railroad gun, naval coast defense gun and provide gunfire support for the naval army.
Naval coast guns and railroad guns were mainly active during WW2 war.
The reason they scrapped on equipping her onto Francesco Caracciolo class is due to limited and shortages of material supply to build the ship.
Naval gun here is a free model from e63papermodel.altervista.org. Model scale is 1/35 with 92mm width , 130mm height and 708mm length.
This is an adult crafts and templates are in PDF with instruction guide in Italy/English.