Language: Iban (Sea Dayak)
Source: Period sources
Description
Duku apang was synonymous to parang ilang, "the decorated Kayan sword".1
Parang ilang was the most widely used name for what we today mostly know as the mandau, the sword of Borneo that is strongly associated with the Dayak people.2
For the main article, see: Mandau.

A fine Kayan parang ilang.
Listed at Mandarin Mansion in 2020.
Notes
1. For mention of parang ilang see among others Ivor Hugh Norman Evans; Among primitive peoples in Borneo; a description of the lives, habits & customs of the piratical head-hunters of North Borneo, with an account of interesting objects of prehistoric antiquity discovered in the island. Seeley, Service & Co Limited, London 1922. Page 292.
2. Anthony Richards; An Iban-English Dictionary. Clarendon Press. Oxford. 1981. Page 15.