Dear Amuk, (is that you first name?)
Pfew... before brookes time. depends on which Brooke.
There is not very much written about these swords.
The oldest picture that I know is from Quer Durch Borneo, so somewhere 1910 ?
Than I believe that I saw more pictures from around 1930' and of course you see very nice examples upto 2000, as on the front of Iban art.
For some reason I think that these swords will not be as old as 1800/1850,
Maybe more around 1900 but that is just a feeling.
Best regards,
Willem