A Deep Dive on Air Mail Envelope Design

We all know what an air mail envelope looks like — or do we?

(Photo via Mollie Lieber West Papers, Women and Leadership Archives, Loyola University Chicago Digital Special Collections)

A few weeks ago I did a deep dive on “Return to Sender” symbols used by the Postal Service. One of the comments on that article came from IC reader Brendan Jang, who wrote, “Hoping for a similar piece on air mail envelope design!”

Of course, I was already familiar with the basic air mail envelope, with its border pattern of red and blue parallelograms (like the 1944 example shown above). But just as it hadn’t occurred to me that there might be myriad variations on the “Return to Sender” pointing hand, it likewise hadn’t dawned on me that air mail envelopes might be a deep well of design diversity. I had intuitively assumed — very incorrectly, as it turns out — that they were all the same.

So at Brendan’s suggestion, I started a journey down this new rabbit hole. One thing I quickly learned is that the classic air mail envelope design is actually patented! The design was created by a Buffalo stationer named Benjamin Dahlke, who applied for a patent in 1927. It was granted to him in 1929.

Note that Benjamin Dahlke’s original design concept called for the border pattern to be interrupted at the upper-right corner, so as not to interfere with the application of postage. (Image via U.S Patent and Trademark Office)

According to Dahlke’s patent application:

[The parallelogram pattern] immediately attracts the eye and serves as a flash or signal, facilitating the duty of giving such mail the special attention required of mail clerks and ensuring the quick and prompt delivery to which such mail is entitled. Furthermore, by carrying this characteristic border around the edges of the envelope, it can be readily detected in a pile, bundle, or stack of miscellaneous envelopes, thereby materially aiding in the quick assortment of air mail, or other special mail.

This illustration from Dahlke’s patent application shows how the air mail envelopes are easy to identify in a stack of mail. (Image via U.S. Patent and Trademark Office)

This design has become informally known as the Dahlke envelope. Although Dahlke’s patent wasn’t granted until 1929, the U.S. Post Office Department approved the use of his design in the spring of 1928. As a result, the earliest known examples of the Dahlke envelope are from 1928. Some of them were manufactured by Dahlke himself and sold at his stationery shop; others were made and sold by other stationers.

This small news item appeared in The Buffalo Courier-Express on April 2, 1928. (Image via StampCommunity.org user wt1)

This is the diagram that the Post Office Department provided as an officially authorized air mail envelope design in 1928. Note that while Dahlke’s patent drawing showed two blank edges in the stamp area, the approved design shows only one blank edge, at the top. (Image via StampCommunity.org user wt1)

Almost immediately, there were design inconsistencies. For example, some envelopes didn’t have the border pattern along the top edge (similar to Dahlke’s patent drawing), while others had an uninterrupted pattern going all the way around the envelope.

Interrupted border at top, uninterrupted at bottom, both from 1928. (Photos by Jeff Mills, American Air Mail Society, via SouvenirsOfSpace.com)

The relative size and spacing of the parallelograms also varied widely. Some border patterns included a lot of white space, while others were more densely packed.

Two different approaches to parallelogram distribution, both from 1928. (Photos by Jeff Mills, American Air Mail Society, via SouvenirsOfSpace.com)

Most surprisingly, at least to me, some of these 1928 covers had the parallelograms leaning in the “wrong” direction!