Source: Contemporary source
Kayamkulam vaal is a type of talwar hilted straightsword that was used by local nobility on the Malabar coast.
Kayamkulam refers to the medieval Kingdom established in the 11th century which was incorporated into Travancore in 1746, after which it became a princely state. Vaal is the local word for a double-edged sword.
A Kayamkulam vaal sold by Mandarin Mansion in 2017.
Very few examples survived or have been published. The most famous is probably the sword of Velu Thampi (1765–1809) who was prime minister of Travancore between 1802 and 1809 and who rebelled against the British East India Company. Another is in The National Museum, Edinburgh, Scotland. It is illustrated on the back of the dust jacket of Hindu Arms & Ritual by Robert Elgood.
Another example is still held in the old Kayamkulam royal Palace in Krishnapuram, a photo is on Wikimedia Commons.1