Watch List notes:

1878-1880, 24¢ Hipolito Vieytes, American Bank Note postal envelope die trial color proofs of the embossed stamp, Comprising, composite proof with two impressions in blue and mounted on small cardboard, plus single example, Very Fine, extremely rare, as we only know about the existence of a similar piece shown in a website called asianphilatelist.org. Higgins and Gage 4.

Estimate: 200-400