Language: Acehnese
Source: Period accounts
Description
The rencong is a typical Acehnese type of thrusting dagger that was often worn together with the sikin panjiang. They feature a narrow, pointy blade and a bulbous hilt, often with a long protrusion in the direction of the blade's spine.1
It is found under various names in old accounts, including rentjong, reuntjōng, rintjōng and rintjoeng.

A typical Acehnese rencong.
Listed at Mandarin Mansion in 2021.
Fischer, writing in 1912, distinguished three main types:

Type A: With a smooth blade
Type B: With a faint sunken section
Type C: With a clearly defined fuller
High quality ornate rencong with golden crowns were part of Acehnese state regalia, presented to local rulers and nobility by the sultan.
Notes to description
1. G. Bisseling & P. Vermeiren; Rentjongs. Tweede Uitgave. Musket, Antwerpen. 1988.
2. H.W. Fischer; Catalogus van 's Rijks Ethnographisch Museum. Deel VI. Atjėh, Gajō- en Alaslanden. Sumatra I. E.J. Brill, Leiden. 1912. Page 141.