Perhaps perm 856? Or started service 858 from Yishun?
S106 856 still 751Z's block.
Think you might want to ask the driver again. I have no luck
with the previous one other than claiming that 585L is an YI bus.
Furthermore the YI roster side is always the same old buses hanging
around on the S-Shift side of WL and some SE duties like 859 and
980 etc.
BTW SMB66X, can I ask is there any conversion of 1 full day
block to split for 911? Since you are living near there?
