These are amusing stamps wrapped up in the history of Julio Popper and his wild adventure in Terra del Fuego.
The stamp was issued by Popper in 1891.They were used on mail to the
Chilean mainland.As Chile had no post office there,the stamp covered this cost.Once arrived at Punto Arenas his agent there further franked the mail with Chile stamps and then the letter entered the Chilean postal system.
The stamps were also used on all mail arriving in the Popper territory and postmarked in San Sebastian.So it had a sort of postage due usage also.(incoming covers only 2 known)
The first printing were Dull Carmine & Carmine Rose,the 2nd printings were Rose-Red & Bright Rose-Red.
These are easy to plate.
I have this block of 25 in Carmine-rose.
The Buenos Aires printers name in full in the sheet margins is:KIDD y Cia Limd SAN MARTIN 351