Well, according to this, the late 70’s/early 80’s was a low of 210 (1977) and a high of 249 (1982). These were the years that I recall because I worked in the foreign exchange department of a major international bank during those particular years.
Looks like it was 296 as late as 1976.
Got any idea what caused the big drop in 1978? I can’t hardly imagine it being “strong dollar” in that era.