To the casual observer most Mk1 vehicles might look all the same, with perhaps only noticing some with different bogies and others with prominent glazing frames and the like however that’s quite far from the reality. Even within the main span of production between 1951 and 1964 and the years following in BR service there were several alterations and changes to the builds, some to correct problems identified fairly early on and others, like air braking to meet the changing needs of the fleet. Most of these changes have been recognised by modellers and those with a specific interest in Mk1’s however occasionally some unidentifiable modification pops up that was applied to a small number of vehicles that escapes identification especially when so few were photographed in service. One that had avoided me till today, was this one;
Applied to Mk1 BSO’s the original bodylights retained by interior wooden frames have been substituted for with the top and bottom lights being held in with rubber glazing sections. The body of course has had to be repanelled to provide the round corners necessary for a one piece glazing rubber for less joints and less leaks, the problem they were trying to resolve. In the late 50s BR eventually settled on one piece external glazing frames as the answer to the problems, all new vehicles being fitted with them from then on, but not before several trials of this nature.
As it turns out (I should have read Parkin’s Mk1 bible more thoroughly) nine BSO’s (9248-9256) had the van bodylights altered to the same arrangement (on both sides) under this modification, note the saloon bodylights remained as originally designed. One vehicle at least 9254, survives on the Kent & East Sussex Railway. Though somewhat altered, several of van bodylights remain as modified by BR.