This link shows a copy of the Nuremberg iron maiden where you can clearly see its campanulate qualities https://literature.fandom.com/wiki/The_Squaw
Noah's Ark sets were a popular item in the 19th and early 20th centuries; the book Youth Cultures in America [2 volumes]edited by Simon J. Bronner, Cindy Dell Clark. states:
Animal shaped toys carved from wood are among the earliest folk toys for children. These range from hand-sized wood horses, for example, to larger toy horses on a wheeled platform to rocking horses large enough for the young child to ride. Adults would also fashion folk toy animals from other materials, including clay and straw. With the emergence of commercial toy companies in the 19th century some wooden toys shaped like animals were mass produced, even if made by hand. A popular Sunday toy in the United States was a wooden Noah’s ark with carefully carved pairs of animals (and Noah and his wife too). Religious parents would let their children play on Sundays only with toys of moral or religious message, hence the popularity of Noah’s ark.
To this I would add my own observation that the parents probably enjoyed the fact that the ark doubled as the storage box and children could be encouraged to put the animals away by sending them into the ark two-by-two.
A number of images of such arks are available online, very many of them having been of German origin, which may also speak to their appropriateness for a novel set in Nuremberg. Although there are many styles, the ones with lathe-turned figures for Noah and his wife would seem to be closest to the iron Maiden in shape.