Doug, I know it's the range of the magazine, but obviously this piece can be dated with a bit more precision than that.
As I understand it a range is given when the piece can't be more specifically dated.
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My avatar is a sketch by my son who is an art school graduate. Some of his sketches and paintings are at
https://www.jamesspaethartwork.com/
He is available to do custom drawings in graphite, charcoal and other media. He also sells some of his works as note cards/greeting cards on Etsy under JamesSpaethArt.