This hollow triangular crossection is very common to see in 19th c. "duelling swords" and 18th-19th c. smallswords. As examples of the later:
Smallsword, French, 2nd empire:
Smallsword, French, late 18th. c:
Today, this type of cross-section can be seen in the direct descendent of these weapons: the sport fencing blades.
So, it's not strange to find it in such a vintage swordstick. Which is very nice, by the way, I must say...
