The so-called triratna symbol was originally not a symbol at all, but a monogram that can be read as namo, “veneration”. The other three (fish, flag, and rotating star), have parallels in artistic expressions of many religious communities of ancient India.

Falk’s conclusion that the “triratna” symbol in Ancient Indian art actually meant “namo” seems, to me, quite conclusive, especially as it is often juxtaposed with different symbols that refer unambiguously to the Triple Gem.

Falk’s further conclusion that the fish, flag, and whirl 🐠 ⛳ 🌀 symbols refer to the lower, human, and heavenly realms respectively (the “triloka”) strikes me as plausible but in need of further evidence beyond what he provides here.