If it is not in Gibbon or Michel, its a fake. As Ray Ceresa said, any “Abroad” overprinted or surcharged mint stamp that is more expensive than the corresponding regular issue for Russia has been extensively faked. I believe he has a whole list of the various fakes. Even ignoring the color (which gives it away), it looks like the serif corners are too rounded to be genuine.
Also, you can check to see if the angle of the overprint is correct, and see if there are any Offices in China cancels with that distorted star. It could hypothetically be a CER cancel, but that would be a lot less likely. Finally, what’s with all the blue smudging? Doesn’t look like a cancel, but doesn’t seem to be part of the printing either.
Well, have you seen the lots that are trimmed arms issue stamps from the 1870s and 1880s? The seller wants $25,000 to $50,000 for those. No amount of talking to him phases him at all, and eBay does nothing.