So! Today in vintage Barbie clothes, we have... half an outfit. The Picnic Set from 1961!
The bundle of clothes I purchased did not include the jeans. (Nor, for any of the outfits, the accessories.) But I had another pair of Barbie jeans to hand, so this is my approximation. All that I got was the blouse:
Which, for the record, isn't actually a blouse! I'm not sure exactly what one should call this, in fact. A leotard? A bodysuit? Overall, it really is an excellent way of making sure a doll's blouse stays tucked in, so I'm going to have to see if any of my patterns has something similar that I can adapt for non-knit fabrics.
And, finally, the hem is simply folded over and topstitched down, as are the armholes. The side seam is unfinished.