Staffordshire dog figurines would be a decent example of something that lots of people mimicked (some quite well). I am not sure of the historical legality, but times were different and those who could often did lol! If you go to Chinatown in NY and know where to look, you can find some very convincing knock-offs (with "paperwork" to "prove" they are real. I guess the thing is, if a maker's goal is just to imitate it makes sense-- a lot of buyers just care about the look or product and not who actually made it. On the flip-side of this coin, sometimes, a lack of ID, combined with certain features is a form of identification lol! So it's all very muddy, but certainly there are valuable items with and without markings.