Malayan Motors was at Leng Kee Rd, not Alexandra Rd.
There were supposedly 2 depots at Bedok. One is Bedok North (4***)
and the other is simply Bedok (2***). It might be possible,
although unconfirmed, that the latter was probably the depot for
Katong-Bedok Bus Service. Located at 638 Bedok Rd (I have no idea
where this is), Katong-Bedok became part of the Associated Bus
Service before the formation of SBS, of which it eventually became
a part of.
3*** belonged to Bukit Timah Depot. This depot was located at 35
King Albert Park, and its site is now occupied by the McDonalds
drive-thru (Macdonald Place). It was the office for Green Bus
Company, which became part of United Bus Service and eventually
SBS. 3*** was later used for Woodlands Depot, which was located
where Kranji MRT now stands.
The use of prefixes makes it easier to record which buses belong to
which depot during the chaotic and messy deployments of the
early-SBS era. For example, SBS 1001 means bus #1 from Alexandra
Depot. However, problems arose when the time comes for depot
transfer. Therefore, SBS dropped this system in favour of a
specific rego range for a particular model. One depot was not
mentioned here and that is Jurong Depot. What was its prefix, if it
ever had one? Was it 7***?