It used to look like this LMS toy coach - a lot better (not my photo)
The actual body shell seems a prototypical botch job, a sort of mk1 shell with makey up side panels pretending to be old world LMS. Don't think any such coach actually ever existed.
Your coach was Hornby's pretty awful repaint of their Caledonian Railway coach - they did two (a compo and a brake third) to run with their Caley 123 loco. The original version was in a reasonable attempt at the Caledonian's coach livery.
I had considered repainting them in mahogany as a cheap and cheerful GNR panelled coach - but never did. 33lima built me half a dozen fifteen years ago which are still thundering round the loft behind my Class WT.
Like the others - I commend you for your handiwork when you were twelve!