Almost identical to the Pressed Steel Class 117s, the design was an update on the BR Derby built Class 116 units. This was a high density layout with a door to each seating bay, with a large guard / luggage compartment in one power car in each set. Updates from the Class 116s included adding the four-character route-indicator on the cab front and a toilet in the centre trailers.
Two marker lights were fitted above each buffer, although the first four sets did not have these from new. Buffers were initially of the square a.k.a. cut pattern, i.e. large round with flat top and bottoms.
The interiors were to a high standard compared with other high density stock built by that time and featured veneered wood paneling throughout as used extensively by BRC&W on the earlier Class 104 units supplied to the LMR. Traditional tungsten lighting was fitted, and large oval mirrors, two at each end of each power car mounted on the paneling between the cab bulkhead windows and the first passenger seat windows on each side.
Though built without corridor connections these were added to all vehicles during the late '60s.
An interesting feature of the class was that after the abandonment of the four character headcode display system, at least one set (P480) had it's front marker lights removed in favour of the fitting of two illuminated white discs mounted in the headcode box as on most locomotives of the time. This situation lasted only until the repainting into blue & grey when headcode boxes were blanked out completely and all vehicles had marker lights.
The images shows 51327 as part of 2-car set P480 with it's marker lights removed and two white dots on the now-disused 4-characer box Ian Francis.
Over the years other types of buffer were fitted - oval and large round. Laterly a number of sets had the roof vents plated over.
Although the Class didn't seem to be part of the "refurbishment scheme" (and certainly never carried the refurbished livery, some sets did receive the refurbishment treatment of fluorescent lighting and extra silencers.