Sometime I do find surprises on
ebay. This is a block of 4 consisting two horizontal pairs of stamps with imperf between the stamps. (Do not confuse this with imperf stamps, with are plentiful at $5 or less each.) This block is also imperf in the top margin. There were only ten pairs produced and I believe this is the only block. Further more, on the back of the stamp, there are pencil notations. "block of 4" imperf vert ??? / ex Hind collection rare / #360 (Scott #) / A O Tittman. Arthur Hind was the greatest philatelist ever existed, who outbid King George on the 1c Guiana at the Ferrari auction. A O Tittman donated his Mexico Sonora collection to the Smithsonian Museum.
http://www.postalmuseum.si.edu/find...ng_Guide.pdf
