The following teaser is from the British Library blog.
The ‘Archive of Yogyakarta’ refers to a collection of some four hundred manuscript documents in Javanese dating from 1772 to 1813, originating from the court of Yogyakarta. A highly important source for the political, economic, social, administrative and legal history of central Java in the late eighteenth and early nineteenth centuries, the archive comprises official reports, letters, accounts and other documents as well as the private papers of Sultan Hamengkubuwana II (r. 1792-1810, 1811-1812, 1826-1828) and his successor Sultan Hamengkubuwana III (r. 1812-1814).
Thanks to ResearchBuzz for the heads-up.