there should be a Dot to mark Pin1. Unfortunately this Dot is missing.
The branding and the missing dot or dimple looks different from standard ADI
branding for SOIC8 packaging.
On these older parts package marking may not have been updated (to standard ADI
marking) , I reference the Bevel on the edge as the locator for Pin 1. From
the picture you can see the bevel on the left side. You can also see the bevel
on the package specification descriptor.
I have attached the SOIC-8 package drawing from the OP90 product page. You can
see the bevel on the pin 1 side of the package drawing. The shading on the left
side of the photo looks like the bevel. The customer can verify this and
compare with attached drawing.