The London & North Western Railway was created on 16th July 1846
from the amalgamation of the London & Birmingham, the Manchester & Birmingham and the Grand Junction Railways.
This merger resulted in the largest railway system at that time in the United Kingdom.
[See David J Froggatt, "Railway Buttons, Badges & Uniforms".]
It is a 2-piece button made by J Compton & Sons, London
with silvered brass front.

Its diameter is 26mm.