Today's US size 12 would have been marked at least 16 if not 18 or even larger, back in the early 1980s,  when catalog sizes replaced pattern sizes for women's clothing . That's when vanity sizing really began . In the 1980s, size 6 jeans meant 24.5-25.5" waist and 34.5-35.5" hips. But in the 1970s, to wear size 5, 5/6, or  6, you needed a 21-22" waist/32-33 hips ! (I know because my sister is 9 years older than me and I got her early 1970s teenage hand me downs) . So a US size 12 in 2019 is what would have been at least 16 in 1983, but in 1973 would have been...Lord, 20? 22? Too big to even be sold outside of a very few specialty shops?  Especially for women under 5' 5"' , it is indeed a large , if not an XL or XXL.