In the early fifties the 16T mineral wagon was very much a replacement for the fleet of decrepit former Private Owner coal wagons so is unlikely to have been seen in any other traffic. There were, though, privately-owned five-plank RCH 1923 wagons and similar-sized steel opens ( some of either ending up with M36xxxx & M48xxxx numbers ). At this time, of course, ballast was often sourced more locally so any suitable-looking wagon to hand might have been used : it was only the Southern that had really long distance ballast flows, in bogie hoppers, from Meldon ........ not unlike the ICI hoppers shipping limestone from the Peak District. Other uses for limestone might involve burning it to quicklime - which required specialised wagons - or tarring for roadstone ( the Southern, at least labelling wagons which were not to be used for anything else ).