I am nowhere near an expert on the Fuji's, but as far as I can see, it is just an FW 17 RC (as far as I know a watercooled .15 with layshaft and reduction) but:
--It is the first one of that type ever that I have seen to be all black.
--The condition of the paint looks better than any other NIB I saw on e-bay but I have seen this type only with off-white tail and brown casing.
--The same seller listed a seahorse type, completely disassembled and the parts sandblasted, just about 1 or 2 weeks prior....
In my humble opinion that combination of facts indicates this motor is not original but completely re-done, most likely very recently.
There have been sold a few incomplete "scrappers" of this type recently, so it is most likely built out of combined parts of different motors. A "Frankenstein" Engine...
I am not a collector. I'd like to use the motors I buy. But an engine that possibly has been sandblasted, possibly has been assembled from different, most likely heavily used ones, represents a too big risk to me. One particle of grit somewhere, one worn out part, and the engine is wasted.
And the price might be fair for what is on offer, but for me way too much.
(But it is really a beauty that's for sale there....)