BR Standard Block Instrument

[Phil25]

Hello. When looking at signal boxes I came across some weird differences. A lot of people probably recognize the famous BR standard block instrument, but I've seen that a lot of them have their TOL (Train On Line) indication on the right whilst some of them on the left. AI I used mentions that the standard position for block instruments is TOL on the right, so I was wondering why are there so many pictures of these block instruments with TOL indication on the left? Below is an interesting picture of a signal box with two such different instruments (you need to look closely).

 

[Annetts key]

There were various block instruments of various designs.

But I'm no expert in this area.

 

[PhilH]

The instruments came in both hands. When BR replaced older instruments with its standard type, it matched the orientation of TOL (left or right) with the replaced instruments so that the signaller would see no difference.