Lot 10031 – 1889-91, “Vicente López” 10p brown, die proof signed by Schirnbock

1889-91, “Vicente López” 10p brown, prepared but not issued, die proof on thin paper affixed to card (150mm x 185mm), engraved and signed by Professor Ferdinand Schirnbock from the South American Bank Note Co. Most probably unique; proofs signed by this Austrian engraver are of great scarcity.