Support! Thank you so much for the comparison between the Yamato and Bandai version. The Yamato VB-6 König Monster was released in 2005. I think the reason you see the 1999 Big West mark on the toy is because the VB-6 König Monster design is from the Playstation VF-X2 game which was released in 1999 and copyright to Big West.
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If I remember correctly, the first Yamato 1/48 was released in late 2002. Any brother can confirm that?