This is a hand blown nesting egg in opal colored glassware, which when held to the light, shows it's opalescent "fire", as shown in picture 3. The size is pretty much the same as a regular egg, as shown in picture 2, with the real egg on the left. I had nearly a dozen of these eggs (as seen in the last picture), but have opted to sell them individually. Price is for 1 white milk glass nesting egg and I have 5 available.
For your country or farm house kitchen, a piece of American history. My Mother would slip one of these under a hen on a nest to encourage her to stay on the nest and lay more eggs. The glass eggs were used for other things as well, like placing inside a sock for mending holes, at which time they were called darning eggs, rather than nesting eggs. Of course, this was back in the days when we needed to make things last. In later years, we just used them for decorating our tables at Easter. My tradition was a small open basket filled with several of these on Easter grass, sitting on the table, with a milk glass hen-on-nest beside it.