King of Mahaderree
This is a very old and well-worn gorget. The holes from which it was suspended are very eroded and the surface is scratched, pitted, dented and corroded. The engraving is so damaged that it is difficult to be certain that the designation is Mahaderree.
The first ‘a’ in the word may actually be ‘y’. The deep crescentic shape, style of lettering and design suggest early to mid-19th century.
John Neville remains an enigma. However, Mahaderree may have been Maharatta Station:
Maharatta. Is situated in the district of Menaroo, N.S.W., 58 miles from Twofold Bay; it is the station of Messrs. Robertson and Throsby. 
Lease no 114, Maharatta, Charles Throsby, non-resident, cattle and sheep. 
The two word endings, -ratta and -derree, are possibly the same kind of suffix or confused suffixes. In the 19th century there was no common method of spelling Aboriginal words and people made up their own systems.
In fact, it is only recently that a common system of principles has been adopted by linguists and there is still variation.
 WH Wells, A Geographical Dictionary; or Gazetteer of the Australian Colonies, 1848, The Council of the Library of New South Wales, Sydney, 1848, p. 247.
 WK Hancock, Discovering Monaro: a Study of Man’s Impact on His Environment, Cambridge University Press, Cambridge, 1972, p. 52