After looking at the detailed pics you included in the openings post there´s a couple of interesting details I noticed as well;
- Difference in height, which was already mentioned.
- Different (deeper) mold marks and on different places (the round dots)
- Odd proportions of the figure (hands are clearly smaller but in relation to that scale the arms seem to be more stretched)
- The 1991 Stamp
All together this is the evidence that´s in line with the thought so far of these figs not being prototypes or test shots like the Laser Beasts discussed in the topic mentioned above in my first reply but that they are indeed Chinese Bootlegs created in China and probably in or close to the original Factory where Takara had the Beastformers made. In 1991 there was no production anymore of original Beasts so that stamp gives away the idea they´re going this bootleg way with the remains of the old molds. In which case its not very strange we see Series 2 and 3 figs only here because those were the figs that´d have been produced until the final days of the line so if there´d be any ¨left over¨ molds its understandable it´d had to be any of the later figs in the line.
I expected the length difference to be caused by the fact they took of a little bit of the foot in thickness, resulting in the absence of the stamp we know underneath the feet of Series 3 figs, but based on these pics that´s not very clear. Another fact that could´ve caused this is a different production condition because we´ve seen before with other BB bootlegs that some are often smaller due to a different material used and or the combination with higher temperatures causing the figs to shrink a little bit inside the molds.
As for the paint that´s applied it´d be interesting to see and find out if the colors that are applied here are in line with any of the colors we know from the original Beasts. For instance is the Green of the armor the exact same color of the Green of the Orangutan or does any of the colors match the colors of an original Beast. Because if that´s the case there´d be a more direct link with the original factory because it´d be hard to match the exact same color tones as the originals and since these are bootlegs they´d probably not have invested to much time in creating the exact colors so they´d not mind if the colors were of. So the color can tell quite a bit more about the origin of them.
The pics clarify a few questions about these Chinese Beasts but there´s still a couple ??? left to be solved, as always