Yard Tugs (YT, YTB, YTM and YTL)

A total of 608 yard tug pennant numbers were assigned during WWII, from 138 through 745, but over 300 of these were for (a) vessels originally built as something else and either converted to or reclassified as yard tugs, (b) acquired from the private sector, or (c) ordered but cancelled.  In addition, many started life as one of the three sub-types and were later reclassified, usually as a smaller subtype, e.g., YTB to YTM: hence the YTB, YTM and YTL columns in the table below.  The yard tug records are sketchy: I will be very grateful for any information that would allow me to fill the gaps in this table.