I've seen a few 1:6 scale jackets by different manufacturers, and while it is possible to miniaturize buttons, seam lines, pockets, etc., the one thing almost impossible to miniaturize is a zipper. There are some very small ones now, but in the 1970s - the timeline Ed has suggested - I don't know of any. "Vintage" 1:6 scale clothing (G.I. Joe/Barbie/etc.) was usually recognizable by the huge zippers on them.
On second glance at the photo, the zipper looks impossibly small.
So does the quilting on the liner.
Any chance of some close up shots of the stitching and details?