Just to confuse things there are two category based classification systems called eclass.
NHS eclass is just the first 3 letters of NSV, there has been some divergence from NSV headings, however most categories are still the same as the original top 3 levels of NSV, and there are still around 2,500
e2class is a more flexible hierarchy than NSV, and so e2class for NHS can support the NHS eclass headings linking down through 4th and 5th level NSV heading to the underlying codes.
Is a 4 level hierarchical category level classification system. It does not go down to individual product items and comes from a background in the German Energy industry. It has a similar number of categories to UNSPSC at 32,832 in release 6.2. However, it has a significant improvement over UNSPSC in that it has standard attributes for categories, and these have been created for over 50% of sub-groups.
NSV and e2class can be completely mapped to ecl@ss, since they have about 20x as much information as ecl@ss. It is only possible to go back to NSV/e2class at heading level from ecl@ss.