The description "morning blouse" indicates to me that this was considered at home wear.
The instructions on the back of the envelope explain how to make a flat felled seam, advising the maker to observe how the sleeves of a man's shirt are sewed into the armhole. This tells us that such seams were common in men's shirts but not in ladies' clothing.
I also thought the collar was interesting (and very nearly fashionable in its day)
Here is a front view of the blouse made up, both without and with the belt:
|From Unsung Sewing Patterns|