Before photography, tracing silhouettes was a hugely popular and inexpensive way of capturing a person's likeness. Even financially stretched families could afford to have a family member stand in front of a light. Their profiles were then traced onto a sheet of paper and cut with scissors. Granted, artistry was involved in the tracing and cutting, for the difference between one person and the next is in the minutest proportions. Should the tracer trace slightly wrong or cut off a tad too much, a different image will result from the original model. Witness these two silhouettes claimed to be of Jane Austen. The first was created around 1800 in Bath.
The second image of Jane, supposedly traced in 1815, shows a more pronounced nose. If one didn't have the illustration of Jane's father to compare to this silhouette, one might completely dismiss it. But one can see a distinct resemblance in the shapes of the noses. If this is not an image of Jane (and the Victorian hairdo and high collar or necklace suggests it is not), one can still conclude that the image might be of a family member. Read more about these two images of Jane here.
Learn more about silhouette making in these links: