An old suitcase containing 15 sketchbooks of ink, pencil and watercolour drawings by Hector French, who drew ships in Leith in Edinburgh, was handed in to Trinity House in the port.
The sinking of some of the ships in Second World War convoys is noted, and on one sketch the word "torpedoed" was written two months after the drawing was done.
Hugh Morrison, collections registrar at Historic Scotland, described the discovery of the works by French, a lithographer who lived near Leith, as "incredibly exciting".
He said: "Not only are these drawings technically accomplished, but they provide a fascinating and unique record of the port of Leith during an interesting period in its history.
"They offer us a detailed pictorial record of ships between the wars and during the Second World War, when a photographic record would have been restricted.
"It is poignant that some of those ships were torpedoed not long after they were sketched in Leith by Hector French."
He added: "He was clearly a very skilled artist, but since we have no other record of his work it appears he simply sketched at the docks for his own interest."
The drawings will go on display this weekend at the maritime museum in Trinity House as part of Doors Open Day.
Pauline McCloy of the Scottish Civic Trust, coordinators of Doors Open Days, said: "This is discovery is like revealing a long-lost treasure that can tell us all a little bit more about the history of Scotland and the talent and skill of its people."