ISTR seeing yellow ends in recent times on brake vans used on engineering
trains (welded rail etc), but can't find any pictures to support this.
The only links I've come across point to fotopic :-(
Are there any markings on the model ?
The OP said it was an "ex LMS" one. So it wouldn't be in LMS livery. It's
entirely plausible that an ex-LMS brake van ended up with yellow ends in
its later days under BR, like the non-(ex)-LMS one in the photo.
Unfotunately you are going for the simple interpretation. He said ex-LMS in
bauxite livery, ex-LMS being 1 second after midnight on nationalisation day.
The new company didnt change liveries for a while but did do some
overpainting especially of grouping letters, hence a bauxite van with extra
markings is quite a reasonable possibility. Add to that Airfix did some
imaginary variations on their stock (see Pat Hammonds book) - but couldnt
remember if that included brake vans. Alternately the OP may have an owner
repainted version - that being a strong possibility - or the wrong model in
the box !
I don't know really then. Even assuming it's an old moulding re-used,
I'm not sure that many or any LMS brake vans survived into yellow end
times anyway. Can you try the LMS Society, I'm sure they must be online ?
Interestingly if you do a google search on images there are some with yellow
ends/markings from collieries. Makes me wonder about this being owner
modified. Does it still have the original number ?