Carolus and Ericus were a pair of identical steel steamers built by Osbourne, Graham & Co.of Sunderland in the post-War shipping boom of 1919. With the usual minute differences in tonnage, they were registered at 2,218 and 2,200 tons gross respectively but each measured 285 feet in length with a 43½ foot beam. Lloyd's Register of 1920-21 records the owner of Carolus as the Ohlson Steamship Co. whereas Ericus is listed as being owned by Sir Eris Ohlson, with the S.S. Co. noted as managers. This was probably some convenient business arrangement at the time of building since the 1939-40 Register gives the Ohlson S.S. Co.as owners of both vessels, with Neilson & Thorden as managers. Originally registered in Hull under the British flag, the 1939-40 Refister also notes that both ships were by then operating out of Helsingfors under Finish colours.

In 1942, Carolus was sold to the Canadian Government, re-registered in Montreal with the Government Merchant Marine Ltd. acting as her managers. Her new career proved short-lived however as she was sunk by a German submarine in the Gulf of St. Lawerence on 9th October 1942 with the loss of eleven crew. Ericus, meanwhile, survived the War, was laid up in 1949-50 pending survey and finally broken up in the UK in 1953.