The Energon Pub

HI everyone! I recently came across a very unusual G1 Star Sword. It has the original stamp © TAKARA.CO.LTD.1989, so it's not a standard knockoff.
The color scheme is very different from the retail version: it's mostly white, light gray, and black, without the typical red and blue details. The color of the plastic appears uniform even inside the joints, suggesting that this may be an original factory test sample or prototype, rather than just a severe yellowing of the white retail version.
I've attached photos of the figure, the stamp, and the Brainmaster block. Could this be a rare pre-production piece? Any information on its origin or potential value would be greatly appreciated! Thank you!