 The first of the latter was D1 542 to D3 685 in 1929, followed by further examples of the D3 upgrade completed in 1930 to give the number range 675-689 and this was further extended to 670-699 by the end of 1932.Later conversions between 1933 and 1946 counted down from 669 to 607 in 1946, and finally 604 ex D2 717 entering service in 1947.It is not clear which, if any, engines were intended to take the slots of D3 605 or 606.