The pin 1 mark is the one on the bottom left of the chip in the photograph.
The marks in the diagonally placed are indentations that occur when the resin is poured into the mold and ejected from the mold. These are called "Eject pin mark".
The pin 1 mark has a double circle shape, whereas the other two marks are shaped differently.
The pin 1 mark is quite small and difficult to see, so we recommend that you use a magnifying glass (etc.) to confirm the position of the mark.
In some products, the Eject pin marks are located differently than shown in the photograph, and sometimes an indentation may overlap the pin 1 mark.