That is not an original Simplex built machine. The gas tank is home built, the frame looks modified to fit the tank. I can't see enough of the engine, but looks like a Honda GC160 to me. I never heard of Simplex building a side car, never saw a literature on one, so that leads me to believe it is not original either.
The wheels look to be worksman bicycle wheels, which are very good wheels, but not simplex!
I don't know how they can call this a restoration and not a home built creation, but people will do anything to get top dollar, even mislead or outright lie!