Help please! Is this an original or just some "bootleg"?

by Karlita
(Mexico)

Hi, every one. Greetings from Mexico! Please, help me to figure out if the one of the right is original or just a repro. See the difference? The one on the left is some old mexican Peaches and Cream I was given at the middle 80's. Of course I'm sure she's original. All 80's barbie dolls I've seen get buttocks like this. The other one (on the right) is a Heart Family mom, recently bought on ebay, but I'm not sure she's original, even she came box sealed with the rest of the family and all accessories. The box looks old and shows some wear, cello is age yellowed (same as the tapes inside), but dolls are kind of strange. Let me explain my self: faces, bodies and hair are beautiful and identical to originals, but some materials seem to be of low quality, and those round buttocks are worrying me, because I've never seen buttocks like these in any barbie doll. She´s marked on back Mattel Inc. 1966 Taiwan. Could be a "bootleg"? or could be some "different" edition or variation? Thank you very much!