A 39T chainring intended for a double crank won't have the triangle alignment mark. It's rotational orientation relative to the big chainring isn't important as there are no shaped teeth or pins. For a 9 or 10-speed ring, the Shimano name, tooth count, etc. engraving should face inward toward the frame. Current double cranks have the shaped teeth, etc. on the big ring to improve shifting to and from the smaller ring. The smaller ring doesn't have or need them.

For a 39T chainring intended for triple use, the triangle should be aligned with the drive side crank arm as the shaped teeth are there to improve shifting to and from the granny.