The 'WT' mark on the BCN indicates that the wagon has been 'Water Tested' i.e. water sprayed on the top would not leak inside, thus making the BCN suitable for hauling goods that are sensitive to moisture. The wagons that have not passed the water test or those which as yet not tested are marked as NWT (Not Water Tested). Cannot guess what the other marking, "WWT" means. Lonand, 2005-08-15. Apurva Bahadur.