In 1908 two _DD_ passenger brakevans were modified for mail sorting use. The modified vans were coded DDMS.
The Car Allotment circulars for 1908 show that the DDMS vans were assigned on the Bendigo line. One van ran on the 0645 Down which formed the 1515 Up. The other ran on the 1215 Down which formed the 1850 Up.
In the 1910 carriage and van recodings, the DDMS class was relettered to CDS with the same numbers being kept.
In 1922 it seems the vans were no longer required for the traffic. They were modified back to standard vans. CDS 1 and 2 became _C__ 47 and 48 respectively.
They could not revert to their old numbers. The 1910 recoding had consolidated the numbers.