Ended.
1985 British Virgin Islands proof $20 (crown sized) with some very cool irridescent (or opalescent) green toning on the fields around QEII's portrait. The coloring of the toning is like dichroic glass, largely brilliant metallic green, but with flecks of purple and blue visible when the angle of view is changed.
The obverse has an image of a jeweled lady's ring with no discernible toning. Guess the reverse was in contact with the paper of a flatpack for 20 years. That's how these were shipped, on a flat card with film covering the obverse and the reverse hidden.
Winner pays $1 domestic postage, or $2 int'l airmail.
Ends 11/15 7pm EST
Addendum:
KM# 51 20 dollars
weight 19.0900 g.
composition 0.9250 Silver 0.5678 oz. ASW
Obverse similar to KM# 48
Reverse Emerald and gold ring
Thanks to Erik for the lookup.