Thank you for your interest Mercenary !
I think the location and the form of the holes is significant to their purpose. When they are present as three in the shape of a triangle they are usually off centered and could have no bracing purpose. In this case they either act as trademarks or have some aniconic symbolism.
Vedic religion encouraged iconography because they believed that God (Ishwar) is formless (Nirguna) and in order to meditate on him we humans, who can only perceive things through our senses, need something which has form (Saguna) therefore they invented deities which represented different aspects of the formless God. The original Vedic triad was Agni, Surya, and Rudra which by Puranic times has metamorphosed into the Trimurti of Brahma, Vishnu, and Mahesha.
The iconography associated with the Trimurti was very precise but there also existed a significant aniconic representation of these deities which served the purpose (as opposed to the iconic) of acting as safeguards against reducing the divine to the level of the human. For example Shiva was represented by the Linga, Vishnu by the Saligrama, and Shakti by the Yoni. Yantras, Chakras, and Swastika would be other examples of the aniconic used in Hindu culture.
The three holes could also represent the three Guṇas (Qualities that make up a living being) - Sattva (Harmony), Rajas ( Passion) and Tamas (Chaos) - also represented by the three points of the Trishula.
They could represent the three main Nadis (Energy channels in the human body) - Ida, Pingala, and Sushumana.
They could also represent the three wheels of the chariot of the Moon - Which could have been of some importance to Chandravanshi Rajputs who claimed descent from the moon.
All this is of course pure speculation on my part. I am just throwing out some of the possibilities. Your guess is as good as mine.
Ian the points you raise are valid. The blade in #42 is currently in my possession.
I believe that the current brace with the fancy koftgari is the newest edition (late 19th century) of a number of braces that this old blade has had. The previous braces ran along the middle of the blade and were riveted through the metal filled holes. I agree with you that the shape of the holes is odd but that could have just been because of the shape of the chisel used to make them. The odd positioning of one of the holes could just be because of a different sized brace that was used in the past. I do not believe that they have any aniconic significance on this blade but I could always be wrong.