Considering that ivory manikins (and some in other materials such as wood, wax, and even marble) were a bit of a fad, and had a history of copies, the question of forgery is difficult. K. F. Russell categorized these manikins, but his research was largely confined to the copies at the Wellcome Collection (and now Science Museum in London) and a few others. Eugen Philippovich did more work on the manikins to determine their origins, but not their differences. I have found even more “types,” but some remain unique.
One of the strangest I have come across is a plastic manikin (the material was confirmed by the owner) sold through an Internet broker.