thewestexit,
When you purchased your Duo did it include the wrap-around band on the box mentioning the free CD's, coupon book, free "mystery" TG-16 chip game (I was told that it was always either Ninja Spirit or Splatterhouse. Mine was Splatterhouse)?
I think TZD took those games out of some of their shrinkwrapped Duo's, and that is why they were sold non-shrinkwrapped in 2000 on. Either that, or not all of the Turbo Duo systems sold in the US included the free stuff inside.
I think if the system had the free stuff inside, it was shrinkwrapped to keep the goodies inside, and also the wrap-aroudn band from being damaged. If there were no free items inside, those may be the systems sold non-shrinkwrapped?