SOB
Ocean freightShipped on Board
Confirmation that the cargo has physically been loaded onto the named vessel.
In practice
A B/L with a shipped-on-board notation and date is what banks require under a letter of credit. A received-for-shipment B/L, issued before loading, is not the same thing. The SOB date is usually the B/L date.
Seen in the wild
LC requires SOB date no later than 20 Oct. Vessel sailed 19 Oct so we are within terms.