Found 3 symbols starting with IO:

Ionizing radiation sign
Ionizing radiation sign
Ionizing radiation symbol
The new supplementary ionizing radiation warning symbol launched on 15 February 2007 by the International Atomic Energy Agency (IAEA) and the International Organization for Standardization (ISO). Con…
Iota
Iota /aɪˈoʊtə/ (uppercase Ι, lowercase ι; Greek: Ιώτα) is the ninth letter of the Greek alphabet. It was derived from the Phoenician letter Yodh. Letters that arose from this letter include the Latin…