Opening windscreens on trains

[theageofthetra]

Was watching a recording of 'The nations railway' and at about 20 mins in there is a clip from the classic transport film 'Terminus'.

There is a very short shot of a 4Sub? at the buffers at Waterloo and it shows a driver opening the secondmans windscreen, leaning out at doing something with the route code. Was this ability to open a front windscreen unique to this type of unit?

 

[yorksrob]

I believe it was quite common on Southern Railway EMU's to enable the driver to change the stencil route codes.

 

[30907]

On a quick browse of photos, all pre EPB units had two different front windows, i presume one opening and one not. The only exception were obviously the Nelsons (COR RES BUF) with offset head code boxes - did they open somehow?