Agree with Michael. There are numerous issues from around the world around this same period that now appear mostly gray. I would suggest put it under high magnification (x50+) and look at the edges of the design images. Do they start to appear more purple? If so, then it's a color changeling. Many of the US revenues printed in the same color, and the Scott #70 and #78 and their variants from US front of book are all highly susceptible to this effect. But the colors can still be determined by the type of fade. This is where strong reference collection can help.
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Many of the US revenues printed in the same color, and the Scott #70 and #78 and their variants from US front of book are all highly susceptible to this effect. But the colors can still be determined by the type of fade. This is where strong reference collection can help.