This 1939 DKW NZ500 is a rare bird, in fact the seller says it's likely the only one in the USA. It's a two cylinder, two stroke in remarkable condition. It's the kind of bike you would be proud to display, but one you could take on leisurely rides through back country roads as well.
The two stroke requires mixing the gasoline and oil and like any two stroke, gives surprising performance for a motorcycle of this vintage. It has a girder front suspension, left side foot shift along with a right side hand shift. Sidecar lugs are present.
The rear swingarm suspension can be adjusted on the fly by turning handles to stiffen or soften the ride. The current owner replaced a long list of items like tires, tubes, clutch, plugs, hand grips, foot pegs and more. It really looks to be very presentable.
These pre WWII era German motorcycles had excellent design and engineering and many manufacturers from around the world freely "borrowed" many of those technical features after the war. This bike would be an interesting addition to any collection. It's for sale on eBay.