The 206 are belt driven (timing belt) and have a bobbin case you take out to replace the bobbin. The closest swing arm zigzagger is probably the 401s and related models. They have the direct drive motor, no belts, meshing gears, and the drop-in bobbin case. I like the early cast iron zigzaggers, I have my eye set on a Bernina, but I am open to other makers, there are a few very nice and interesting models made from around 1930 to early 1950s.