The Two-Speed Shinkansen (2スピード新幹線) is a new power model of the 100-series Shinkansen from 1987 that uses the two-speed new power gearbox. It was first released in the new-for-1987 6th generation packaging. The 100 series actually post-dates the 200 series Shinkansens and were introduced to Hikari service on October 1st, 1985. The 100-series Shinkansen was first released with an old power gearbox in 1985 as the New Shinkansen with a front light similar to the Hikari with Light. At the time of its release, no other Shinkansen trains were available with a two-speed gearbox, although 300, 400, and many other later Shinkansens were released with two-speed gearboxes since. My Japan-made early two-speed 100 series comes from the 1987 2-Speed Shinkansen 3 Dimensional Station Set.
The early Two-Speed Shinkansens were made in Japan and have black power switches and gears in the gearbox as well as brass contact strips. These trains were produced between 1987 and 1989 or so when 100-series production moved to Thailand. The new power molding is based closely on the old power molding which also included a light feature, most of the parts of which are still present in the molding. I would like to add a light into a new power 100-series some day, as I do not think it will be particularly hard.
I have recently acquired a second Japan-made two-speed 100 series with black power switch. I used a grain of wheat bulb as described here to add a light back into it, creating the ultimate Japan-made 100 series, with a two-speed new power gearbox and light. Admittedly, the light is still a little hard to see...
The intermediate and tail cars are constructed similar to other cars of the era like the 0 and 200 series cars, with the intermediate car chassis matching the mid 1980s remote control trains' intermediate cars like the old power New Shinkansen with Light (I have even seen an old power 100-series converted at the time to run with a 1980's remote control receiver and gearbox). The intermediate and tail cars both use the more secure axle holders that had been in use for several years already and have the single split loop couplings of the era.
When Plarail production moved to Thailand around 1989 the power switch and gears were produced in white plastic instead of black. Black power switches could still be seen on some later box art like the 1989 Thailand reprint of the 1987 2-Speed Shinkansen Set.
Very little is different between a Japan-made and an early Thailand-made 2-Speed Shinkansen - the toolings have been changing to say Thailand, the colors of the gears and power switch have changed, and the contact strips are no longer brass. Two of my Thailand-made 100 series do not have production stickers. One likely predates the ~1990 introduction of the production stickers as it comes from a 1989 print copy of the 2-Speed Shinkansen Set. The other one may have originally had one but lost it over the years. The third 100-series power car is marked with D1, meaning it was produced in April 1991. Some time around 1993 or 1994 the power switch and gears would have changed to the light blue plastic used from then into the later 90s.
This style of two-speed 100 series was also exported to Germany as part of Tomy Express Set 02. These trains were all Thailand-built and remained in production into the early 1990s. Other than the text on the power car, they are the same as regular Japanese-market 100 series from the early 1990s.
The 2-Speed Shinkansen was rereleased in seventh generation packaging in 1994 and remained in the lineup until 2002. When the range was refreshed for 2003 an updated 100 series was released as S-04 100 Series Shinkansen which was discontinued in 2014.