₿ i.c.o.

On this day in 2009, the first initial coin offering took place with commencement of the Bitcoin blockchain by the individual or group called Satoshi Nakamoto, creating fifty of the virtual units of account as fiat tender.
As far as sub-divisions go, one-thousandths of a Bitcoin is a millibitcoin and a hundred-millionth is a satoshi.  The peer-to-peer currency exchange (open for business ten days later) independent of central banks and intermediaries featured a public ledger that cryptographically records transactions, but its origins are somewhat murky with a good deal of speculation as to the identity of the inventor, which—antithetically—includes one Elon Musk.