Leo got back to me with this answer and two scans:
In response to your query, it is important to distinguish between precancelled stamps and stamps used for bulk payment. I doubt very much that the stamps in the image attached to your email were intended to be used as precancels. It is possible that the stamps were used for bulk payment, but the examples of bulk payment I've seen were cancelled by a roller cancel while still in complete panes.
I think the stamp were most likely used for one of the following:
1. Payment of circulars. Some post offices cancelled the stamps on the circular bulk payment forms with a cancel date stamp, others with a roller cancel, and some with a crayon cancel. See the attached circular bulk payment form cancelled at Clinton, ON, for an example of crayon cancels very similar to the cancels on the stamps in your image.
2. Money tags.
3. Fiscal usage. It is true that the War Tax on cheques was 2c except for a brief period, but the War Tax could be much higher on other payment instruments. On the attached example, the tax was $23.54, and the stamps were cancelled with a crayon cancel.
Hope this answers your questions.
