Asking where this bicycle sits in the hierarchy is like asking where a Miyata 1000 sits in their hierarchy. Neither firm provided a strict hierarchy, instead grouping the bicycles by intended purpose. The only way to place them in the overall hierarchy is by price but even that is somewhat misleading, as the touring model prices are driven up by factory included accessories such as bottles, cages and the rear rack, which were were not part of a road bicycle package.
While the serial number is from 1983, this could be a 1984 model, as it is also a very good match for that year's catalogue. The MSRP in 1984 was $474.95. Nishiki's other grand touring model that year was the Cresta, at $359,95 US. The Seral was a intelligently spec'd grand touring model that kept the price just under the magic $500 barrier. At the time, many cyclists considered this to be the dividing line between a mid-range and high end grand touring bicycle.
While the Seral may not have some of the features of higher end models, they did luck out by specifyng the SunTour Cyclone GT derailleur. At the time, the Cyclone GT was considered on the light side for grand touring and many manufacturers chose to spec ATB derailleurs, with SunTour's sophisticated. dual parallelogram Mountech being a favourite and considered far more suitable for grand touring. Ironically, few MounTechs survived much beyond a year due to poor seals for the 2nd parallelogram.