Dahlke envelope
noun/ˈdɑːlkə ˈɒnvəloʊp/ · /ˈdɑːlkə ˈɛnvəloʊp/
Etymology After its designer Benjamin Dahlke. In use in the late 1920s, the name was patented in 1929.
1
An airmail envelope with a distinct pattern of spaced diamonds in alternating red and blue colours around the outer edge.