Seeking some help in identifying a Model 1917 bayonet marking

[22SqnRAE]

You haven't shown us the scabbard mount/mouth-piece. I'm guessing that it's the American M1917 scabbard with either of the 2 versions of mounts/mouth-pieces rather than the British 1907 scabbard used with the Pattern 1913 bayonet. I would speculate that the "AD star" may be a manufacturer's mark of the leather scabbard?

Thank you F10. I'll post photos in response in another comment.