Ok, I found an old thread...
This link is for an old thread that goes over the history of early Sebo's starting with the 350 (The original Versamatic that Bisonian is referring to.) and the 360 Electronic. Known over here in the states as the Windsor Versamatic.
This is an excerpt from Sebo's official catalogue. (The one in the image, posted above this.)
In 1978, two engineers founded SEBO in Velbert, Germany. Since then, SEBO has become the most important manufacturer of high-quality, commercial vacuum cleaners in the world, with sales in Europe, Asia, Africa and North America. Millions of SEBO vacuums have been sold to hotels, hospitals, schools . . . even The White House!
SEBO’s first shipment to the U.S.A. was in 1979, which was for commercial-cleaning customers, followed by its duo-P Cleaning Powder in 1984, and its household vacuums were launched in 1997. Today, SEBO stands as a synonym for high-quality vacuums in commercial and retail markets worldwide.
Sebo's "shipment to the U.S.A." was the first shipment of Windsor vacuums.
This means that Sebo US was established in 1997.
I thought this important to post as it has release dates for each of the various models.
Here's that link to the thread.
https://www.vacuumland.org/cgi-bin/TD/TD-VIEWTHREAD.cgi?17090