Found 8 symbols starting with OI:

Oikoumene
Symbol of the World Council of Churches.
Oil
An old archaic alchemy symbol for oil.
Oil (alternate #1)
An alchemical symbol used to designate oil.
Oil (alternate #2)
An alchemical symbol used to designate oil.
Oil (alternate #3)
An alchemical symbol used to designate oil (especially olive oil in this case).
Oil (alternate #4)
An alchemical symbol used to designate oil.
Oil (alternate #5)
An symbol used in 17th century alchemy to designate oil.
Oil or gas well
Japanese map symbol for oil or gas well