Another object I have had for years. Always kept because I have no idea. Just felt right. Dont think it is stone had thought maybe bakelite its hard.
It may be a dummy egg - "Perfect for training your chickens on where to lay their eggs. When there are eggs in your nesting boxes they will learn to lay their eggs right where you want them. This trick has been used for many generations, is proven and works great. Using dummy eggs also helps keep chickens from cracking there own eggs. When you plant dummy eggs in nesting boxes the chickens will naturally peck at the egg in the beginning. This is a good thing as when they are ready to start laying there own real eggs they will have no desire to peck the real eggs. Some customers are convinced that the dummy eggs encourage the chickens to lay as well!" https://www.chickencoopcompany.com/products/artificial-eggs-set-of-2
Somewhere around here I have a butterscotch bakelite egg I got at a yard sale. If I remember correctly it's the size of a rather small chicken egg (approx). Mine is a slightly different color on half and at one time I found an example of a bakelite egg in a bakelite eggcup so I'm thinking that's what mine is, missing the eggcup. It would help to know what yours is made of. I have seen them called darning eggs and with the long scratches on yours I'm wondering if that's what yours has been used for. Here is an example of one that I've saved that they are guessing might have been a darning egg. Not the color of yours but it is the color of mine. https://www.etsy.com/listing/285669...how_sold_out_detail=1&ref=nla_listing_details
The dummy eggs are also made in brown and green, because some chicken and duck eggs are those colors.
Best answer so far. It really feels like bakelite I have rubbed it and there is an oder but not like one I have smelled of other known bakelite. Its kinda heavy like bakelite.
It won't harm them and it will give you a positive ID, Google for how to do it and see sample results