One of my favorite aspects of Delta has always been their earlier badges. Because they spent so much time fiddling with one new logo after another in the 1930's, there is quite a variety.
In the early to mid 1930s Delta would use a decal that had "Delta" within a blue banner. This decal would continue to appear on Delta tools for awhile even after several new badges were introduced.
In 1936 Delta introduced their first metal badge. It was a beautiful round logo and the first adaptation of a triangle to represent the Greek letter "Delta". It's also when Delta started using the full "Made in the United States of America" which I think is awesome. Since this era was "pre-serial numbers", the type badge on your Delta can be used to narrow down the year it was produced.
For 1937 the new badge was modified and much of the black was switched to red.
1938, modified again.
Delta made a dramatic change in 1939 and abandoned the triangle and banner design altogether. This rather plain logo would span 1939-mid 1941
In mid 1941 Delta changed their logo back to the triangle again, and now made the city of Milwaukee a big part of the design. This lasted until the employees in Milwaukee went on strike in 1952. By 1945 Rockwell had already purchased Delta and since "Colonel Rockwell" had vowed to close up shop rather than deal with strikers, in 1952 he did just that and moved all Delta production out of Milwaukee. This badge lasted from 1941-1952.
In 1947 during the time of the "Delta Milwaukee" badges, serial number plates appeared that indicated Delta was a division of Rockwell Manufacturing. Prior to this plate there were plain aluminum plates that changed material often during the war. Brass, steel and oil boards were used at various times between 1942-45
Here is the redesigned badge that lasted from 1953-1966.
Delta / Rockwell would go on to have many more badge changes, including dropping the name Delta altogether in 1966 to go with "Rockwell" and eventually Rockwell International would follow in 1973.
Of some interest, Colonel Rockwell's son took Rockwell International in a completely different direction, selling off Delta to Pentair and by the 1980s becoming one of America's largest defense contractors (B-1 Bomber) as well as NASA's biggest contractor with the Space Shuttle. But the cold war did end and the Space Shuttle program became too expensive and Rockwell International went from #27 on Forbes largest companies, to defunct, sold off in bits and pieces.
Aside from the many logo design changes, there are also countless different badges for motors, pulley guards, pedestals, etc. If you have a unique or uncommon Delta badge or decal, lets see it!