The last patent date on the envelope is 1925. Although nominally a sunbonnet, compared to Butterick 5340 which admittedly is a little earlier, this is a much more stylish interpretation.
The most interesting element of this pattern however, is found in the descriptive text on the back of the envelope, which reads
Sunbonnets are extremely smart for those who oppose the sun-tan vogue. This charming model has a gathered crown, and a wide brim trimmed with ruffling. The ruffling may be omitted and a trimming-band arranged over the brim. Elastic is inserted through a casing stitched underneath the crown extension which forms a ruffle. Tie strings tie under the chin.
That first sentence tells us a lot. Tanning was indeed becoming a vogue in the 1920s amongst trendsetters like Coco Chanel who was designing casual but very smart clothes that looked great in sunny places like the Riviera.
But the editors of the Pictorial Review must have felt that not all of their readers were ready to jump on the tanning bandwagon. Even in the supposedly egalitarian Unites States, there was apparently still a sense of the class distinction imparted by maintaining fair skin.
In fact, this elegant little bonnet won't provide much protection from the sun. The brim is fairly narrow, and the little frill at the back won't prevent one from getting a good sunburn on the back of the neck.
Here's the back of the envelope:
This is a beautifully produced pattern. Not only does it include the Pictograph, a tissue sheet of detailed instructions, but each printed pattern piece very sensibly includes instructions for that piece, something I'd love to have on patterns today.