The locomotive pencil drawing below the main image is a saddle tank locomotive, a model regularly used in quarries to transport the stone.
Swanscombe in Kent was one of the largest cement quarries in Europe, it operated from 1792 until it finally closed in 1990. it is now the site of the Bluewater Shopping Centre. Mavor and Coulson (M&C) were Glasgow manufacturers of mining equipment, in 1940 they made a sectional belt conveyor, as illustrated by Badmin here. Because of the prominence of the M&C conveyor belt, It is likely that Badmin was commissioned by them to produce an advert, of which this is the preliminary drawing.