Could it possibly be a misprint? There is a purple line that extends down from one of the face's eyes to its mouth.
It is most likely on the portrait for Agnes MacPhail. I have seen ink smears on the $150-10 with much greater frequency than otherwise noted on BoC banknotes (all be, it is still uncommon and I believe it could be one of the reasons for the inordinately larger amount of missing notes in the sequential bundle). As has been noted in the E2 category in GPMC it is probably caused by incomplete wiping of the plate (intaglio) between rotations. Some of these "lines" are faint but some of them prominent.
When these streaks are located at some specific positions on the portrait they create some very collectible art - e.g. Agnes Mcphail crying with tears from her eye.
If you are able to share your picture it would be highly appreciated as I am keeping a collection of images for a possible future publication on unintended art on banknotes.
