Look for vintage Barbie dolls, which are created with metal pipes, if you can hear the number of collectors, a collector Barbie doll with vintage metal pipes in them. This is very important to always tip and I mean always, the brand of doll you would be surprised how many refuse to check on the market, Mattel, Inc. brand.
These are important steps for fife in the world of classic Barbie doll collection, it is a great hobby and a wise investment, Barbie dolls are more rare every day, so your dolls increase in value.