THE ORIGINAL BARBIE TWIST AND TURN (1966)HAS A SLANTED WAIST WHICH DIFFERS FROM THE MORE MODERN STYLE BY BEING STRAIGHT ROUND.HOWEVER MANY OF THE MODERN BARBIES HAVE 1966 ACROSS THEIR LOWER BACKS JUST ABOVE THE BOTTOM.THIS DONATES THE YEAR OF DESIGN NOT THE ACTUAL DATE OF THE DOLLS CREATION.THE ORIGINAL 1966 DOLL HAS THE DATE PRINTED ON HER RIGHT BUTTOCK.(WITH HER FACE AWAY FROM YOU) AND IS ALSO MADE OF A SOLID HARD PLASTIC AND DOSE NOT HAVE THE BENDY JOINTS, THIS CAME IN MUCH LATER.THE NECK OF THE ORIGINAL BARBIE ENDS IN A SOLID BALL WHICH MAKES THE HEADS EASY TO REMOVE, TODAYS BARBIES OFTEN HAVE THEIR HEADS SNAPPED OFF DUE TO THE NEW FANGLED RIVITY THING THEY ATTATCH TO THE NECKS.THE OLDER BARBIES DO NOT HAVE THE SHINY BLOND HAIR EITHER AND NO MAKEUP TO SPEAK OF.THE VERY FIRST BARBIES THAT CAME OUT IN THE LATE FIFTIES HAVE A SOLID BODY WITH NO TWISTY WAIST.BUT HAVE SAME ID ON THE BUTT THOUGH.YOU WILL ALSO FIND THAT SOME OF THE OLDER BARBIE BODIES MAY HAVE YOUNGER HEADS, LIKE A 1966 BODY AND A 1968 HEAD(DATE CAN BE FOUND ON RIM INSIDE HOLE OF THE HEAD).THIS IS BECAUSE MATTELL USED THE OLD BODIES UP BEFORE MOVING ON TO THE NEW ONES.THIS IS ANOTHER REASON FOR THE BARBIE BODY BANK SEEN ON EBAY, YOU CAN MIX AND MATCH THE GOOD BITS AND GET A DOLL WORTH KEEPING.MOST OF THE SO CALLED VINTAGE BARBIES SOLD ON EBAY ARE ACTUALLY THE MORE MODERN ONES.I HOPE THIS INFO HAS BEEN OF HELP.