Though the “set-mundu” consisting of two pieces of cloth is considered the traditional attire in Kerala, in practice its fairly common to see the lower half i.e. mundu alone in many 20th century photographs. This is usually worn with a jacket like blouse or sometimes a saree blouse as in the 1965 film Chemmeen. Typically the mundu is a woven cloth of cream or off white with a border. While the border can be a simple coloured band, the festive version has a woven gold border and is called kasavu.
You can see the kasavu mundu worn with a blouse on three of the women in this photograph of the Travancore sisters and others. Of the three sisters in the middle, Lalitha on the left wears a neriyath (the upper part) as part of a half-saree like ensemble. Ragini wears a mundu and velvet jacket and Padmini on the right wears a half-sari that is common in Tamil Nadu (in the 50s this was usually a silk skirt, a georgette upper part and an embroidered blouse).
Photograph circa 1954 courtesy Betsy Woodman. L to R Ambika, Lalitha, Chandran, Ragini, Betsy’s dad, Padmini, Sukumari.