Livery button?

[Denny45]

Is this a livery button? Was it used for police, military, railroad or something else?
Back says J COMPTON & SONS LONDON

 

[Outta Place]

Says "Invalid Link"?

 

[Iron Patch]

Not livery, and railway would be a good possibility.

 

[Denny45]

Not livery, and railway would be a good possibility.

Yes, it looks like a railway button because of the letter R for railway and S for south. But what do the other letter(s) represent?

 

[Denny45]

Not livery, and railway would be a good possibility.

Yes, it looks like a railway button because of the letter R for railway and S for south. But what does the other letter(s) represent?