According to a site that explains the trademark/copyright stamping, the shared (Hasbro & Takara) stamping with the made in China indication is used on late 89 Micromaster, Euro-Classics and re-issues.
http://www.fredsworkshop.com/vstampings2.html
Hasbro/Takara-China (Plain)
Hasbro/Takara-china (Kanji and Dates)
-Standard shared stamping, however the location of manufacture is now China instead of Macau. Late 89 change for the Micromasters toys, Euro-Classics line, as well as being the stamping of choice for reissued toys.
-Can be standard, or 'In-Box' stamping (raised platform).
-Many people don't value a European Classic the same as its original counterpart in the same condition. They might as well be called what they are - G1.5 rereleases.
Japanese Diaclone should only have a Takara logo (usually in a circle or something similar).
Maybe yours isn't a Japanese Diaclone? According to some articles GiG had the license for Diaclone in Italy and apparently they were selling some Diaclone even after Hasbro had picked up the license to start making Transformers so that may have been a running change. Or could it have been repaired with parts that had that stamping?
