The class 377/6s and 377/7s were delivered with a single section of first class in one driving car per five car unit. It covers approximately two thirds of the coach and includes a door vestibule. The section is enclosed by sliding doors within the coach.
From delivery until now, the only external indication of its location in the unit has been the small window stickers, which are only really any use when adjacent to the platform. There had been no external yellow band or "first class" lettering beneath the windows. These units operate largely on 'Metro' workings where first class does not apply, but have a number of workings on longer-distance runs (e.g. Horsham via Redhill) where first is in use. The first class seats are supposed to have anti-macassars fitted when in use as such, and removed for 'Metro' workings, but this simply does not happen.
There has been much confusion among passengers (and some staff!) as to whether first class applies - on my Dorking to Victoria train this morning (a 'Metro' working), people were sitting in first, looking around, then moving, even though the accommodation is de-classified on these workings. The reverse is common on workings where first class applies!
377618 now has external yellow banding plus the large "first class" lettering below the windows. As I mentioned, I don't know whether any internal changes have been made, but my view is that, given that they were planned to be used on both 'Metro' and longer-distance runs (including some to Brighton) they should have been delivered with full external labelling and with internal electronic signs in the first class sections to indicate whether the accommodation is being used as first or standard class on any particular working. Until now, the situation has been an easily-avoidable mess.
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On my train this morning (0831 ex-Redhill), the guard was very efficient at checking first class after every stop (it was a single 377/6). He must have re-directed at least ten people who claimed not to know it was first class (some people were obvious as 'trying it on' because they went to move to standard, saw it was more crowded, and then just sat down anyway before being moved!).