The narrow-gauge rolling stock classification system is based on the Victorian Railways broad-gauge classifications.
With the prefix letter N to indicate a narrow-gauge car, each class of vehicle originally had code letters similar to its counterpart on the broad-gauge, and all having bogies, most were double-letter identified, e.g. NBB, NABAB, NUU, NMM, etc. The double-letter classification was dropped with the general simplification of V.R. passenger car coding in 1910.
The letters following the N prefix refer to the vehicle's use and type. e.g. A was used to indicate first-class passenger accommodation, B was used to indicate second-class passenger accommodation and C was used to indicate Guard's Van/Brake Van.
Numbers started at 1 for each class of vehicle and progressed in numerical order.