I'm pretty sure most of my childhood chap meis had symbols (I discovered them in the later years). I know that there are are earlier ones without, their babies were also larger than the newer ones for some reason (I'm guessing they reduced the baby size so the ring saddles would fit them) The older ones had multiple hair colours(? at least mine did) and no symbols, then changed to unique symbols with some with multi hair colours, then went to one hair colour (usually same as body colour) and that same symbol pictured, before selling off the mould to what appeared to be a dollar store supplier, because that was where I got my fakies.
The fakies also had body colour matching hair colour for the most part, and their symbol was slightly more blurry (and usually navy-coloured), as well as being without the chap mei stamp and the baby pony. They were a squishier, thinner plastic too, or in some cases a more brittle thin plastic. The eyes were often mis-aligned, too.