There are some OBVIOUS differences in the times your PC doll was made. this Site has tons of info on dating correctly ( though you may still be off a bit).
AG Wikia says this about the dolls. You can see noticeable changes over time and as Mattel started to mass produce the dolls more in China. Here you have 3 pre-mattel dolls ( PM) and one transitional doll. Can you tell?
This KIT is slightly earlier than Samantha- her coloring is more like a paint and her hair is dry and brittle. All these dolls have soft brown lashes.
This stamp is a good indicator of a Transitional ERA Doll. she could have been made in 1997-2000. My guess is nearer to 2000-02 before they did away with neck stamps altogether.
notice the trans doll on right has darker- less soft lashes and you can see the difference in color in the makeup! See how Kit's lashes seem thinner too? well. Have fun DATING/AGING your PC doll and enjoy learning all about the beginnings of PC dolls!