Cruising in Gulf of Finland

is that an L40/70 Bofors Anti Aircraft gun

Most probably is, i don't have any good source of info about Finnish Navy guns, so i can't be sure. But it sure looks like Bofors
"The patrol boats were built to counter spirit smuggling along the Finnish coast. In peace time they were armed with one 20 mm gun. The older boats had Danish Madsen guns, but the series VMV 8 to VMV 17 had Finnish guns by Lahti. In Winter War the armament was fortified with machine gun, depth charges and smoke screen aggregate. In Continuation War the armament depended on the role of the boat. In 1941 they had 20 mm guns, machine gun and depth charges. In addition they could take 4-5 mines or two 45 cm torpedoes. In 1942 and later some boats were used as gunboats. They were armed with 40 mm and 20 mm guns, machine guns and depth charges. Some boats were used for submarine hunting. They were armed with 20 mm guns and depth charges"