Nummer: 00713
| Area : | Western Area |
| Sea area : | North Sea |
| Date of attack : | 01.12.1939 |
| Time of attack : | 04:53 |
| Nationality of U-boat : | German |
| U-boat : | U 21 |
| Commander : | Frauenheim |
| Grid : | AN 1895 |
| presumed target type : | Steam Freighter |
| presumed tonnage : | 5000 BRT |
| presumed result : | sunk |
| Number of torpedoes/mines : | 1 |
| Used weapon(s) : | Torpedo(es) |
| Date of observation : | 01.12.1939 |
| Nationality of target : | Finnish |
| Actual type of target : | Steam Freighter |
| Name of target : | Mercator |
| Year of launch : | 1904 |
| Actual tonnage : | 4260 BRT |
| Actual result : | sunk |
| Position of target : | 57.25n 01.35e |
| Footnote : | Lloyds War Losses describes the loss position of "Mercator" as 57.25n 01.35e. This position matches with the attack position of U-21 in grid AN1895. - The attack position of U-31 ist given as grid AN4547. This position is nearly 57.39n 00.36e. "Arcturus" was en route from Burntisland to Trondheim. |
| updated on: | 00.00.0000 |
| Remark: | Pos |
| Changes: | 1) Baird 08.1998: Pos. Mercator = 57.25n 01.35e |