In fact, the Toyco in question was and still is a Japanese company. This is the actual website http://www.toyco.co.jp/company.html.
The original Astro Magnum clearly shows a Toyco head office address in Tokyo on the packaging, and both the original 'laser gun' packed version, and the latter 'robot' packed version were manufactured in Japan (as per the box and stamping on the battery cover). The trademark is of course, unmistakable.
The Astro Magnum toys were manufactured and distributed in Japan by Toyco. The figure was then licensed to other parties. As we know, Shockwave was initially released to western markets as a Transformer by Hasbro prior to Christmas 1984, and was part of the Japanese toyline in 1985. Radio Shack, a subsidiary of Tandy, also released a version known as Galactic Man at roughly the same time internationally through its network of stores. When the figures were licensed to Hasbro and Tandy, (as well as other US toy companies), it appears that manufacture was off-shored to Seoul, to a manufacturing partner called Intecs, Ltd.. Both Shockwave and Galactic Man are stamped 'MADE IN KOREA', and there are references to being made in Korea on the packaging and papers included. However only on the back of G1 Shockwave is it clear who the manufacturing partner was.
I can only surmise that the manufacturing was moved to Korea for reasons of production capacity or economics. No doubt the contracts with American companies called for high volume at low cost. Hence, Shockwave, Galactic Man, and other licensed versions were all made in Korea, but still bear the Toyco stamp.
Let it be clear, Toyco was the licensor, responsible for the design and manufacture of the original toy, and have acknowledged it here in a roundabout way, although there are questions as to what parties have rights to produce and market the toy today, even if the mold's whereabouts were known. Hasbro of course would have strong interests in the intellectual property and likeness of Shockwave, though it does not have exclusive rights to the Toyco-G1 toy itself. Hasbro/Takara continues to make toys in the likeness of Shockwave today. And of course the mold appears to be missing.
As a matter of rebuking further the idea that the figure originated in Korea instead of Japan, it doesn't make sense to me that Intecs of Seoul owned the mold in the first instance, or that Intecs and Toyco were in some way a subsidiary of the other, and that the first Astro Magnums were manufactured in Japan, only to revert to Korea when international demand exploded. During the 80s Japanese toy companies generally made toys in Japan, for Japan. The Takara-developed Transformer toys were all initially made in Japan, and in accordance with the operational and financial realities of distributing the toyline internationally in partnership with Hasbro, certain toys were produced in countries such as Korea, Thailand, Taiwan, Macau, France, and eventually preominantly in China and recently Vietnam. The idea that Toyco is Korean seems to be the result of flawed deduction supported (understandably) by a single piece of erroneous data - the website.
Regardless of whether the the figure was produced in Japan first, or Korea second, all the versions considered to be legitimate licensed toys are so because they bear the Toyco stamp on the figure, and Toyco is a Japanese toy company that has been in existence since 1981 until today.