[mastophilus]

As far as I can tell, thong panties didn’t go really mainstream until the 1990s. Although they’ve been around much longer, mostly as “special occasion” lingerie and stripper gear, it seems that only in the last 20 years or so would large numbers of women actually wear thongs as daily underwear. In my high school days of the early ‘90s, a girl might wear a thong to prom, but string bikini panties were usually the skimpiest underwear a girl would wear on a daily basis.
Here’s your challenge:

What’s the oldest movie you can find in which a woman on screen is wearing a thong as underwear? Thongs worn by strippers in scenes set in a strip club can be their own separate category.

Here’s my entry: These two extras in the legendary (in ENF circles, anyway) prom scene in Zapped!, which was released on July 23, 1982 (I got the release date from IMDB.com).

Can anyone find a thong earlier? If you can, post a screencap and the release date of the movie. Maybe post the country of origin of the movie, too. I wonder if the Europeans were distinctly earlier or later than the Americans in this regard.