asdf wrote:

Which, on the Met, are carriages 2, 3, 6, and 7.

They are the 6xxx series vehicles. Each 4-car unit is formed by two pairs of
cars, one motored driving vehicle (5xxx series) and one trailer vehicle,
with compressors (6xxx series). Not all of the driving motors are OPO
fitted, those that aren't can be easily identified as the front ends
continue the paint scheme carried on the sides of the vehicles, rather than
being painted red.