Oooh! Stephenson Clarke, Bargoed. Cambrian, Ely valley. Tirpentwys, Pontypool, PJJP, Pontypool, Any of the 10,000 wagons, run by 1,000 collieries, Coal factors, railway companies, shipping companies, industrial end users, chemical end users,, etc. The delightful little Peckett was a local locomotive to Tymawr colliery, Pontypridd until the early sixties.
If you type in any of the collieries, Google will come up with the Welsh coal mining pages. These are listed by county, so Glamorgan, Monomouthshire, etc will be readily to hand. Happy hunting!
Ian