I'm using the STM32F105, in a LQFP64 package. It has two circular markings, on opposing corners of the IC. This picture is for a different ST ARM, but the markings and silkscreen are similar:
The larger mark in the upper-right of the picture has a flat bottom, whereas the smaller mark in the lower-left is slightly concave. This package doesn't have an exposed pad, so there are no clipped corners underneath.
The datasheet only mentions one mark:
and I haven't found any other package documentation that mentions it.
Does anyone have a clue for me?
The project is completed and the answers are correct. Pin 1 is the smaller, concave mark in the lower-left. Don't forget to upvote the good answers!
Interestingly, I've since purchased another batch of these chips and they only have the one mark. Thanks, all!