Class 455s have blinds at the front indicating the route of the train (although this is rarely correct). These display a number at the end, e.g.: "Guildford via Epsom 16" "Chessington Sth via Wimbledon 18" "Kingston via Richmond 21" "Hampton Court via Surbiton 30" "Waterloo via Kingston 24" "Waterloo via Kingston 32" "Guildford via Cobham 42" It is not present on the Southern units, which have had their gangway replaced with an air conditioning unit. It is also not present on Class 456s (the later, smaller version of the 455s with different traction equipment & bodywork), which suggests that the system was no longer in use by the time they were built. They have a dot-matrix which only displays the destination (unlike the 455 blinds it is usually correct). It doesn't look like a headcode, which usually has at least one letter. I thought it may have been a timetable number, but according to Timetable World the aforementioned services would all have been in tables 77 & 78, & the numbers I have seen on class 455 displays don't go up that high.