VERY FINE. A RARE EXAMPLE OF THE 6-CENT 1895 "USIR" WATERMARK ERROR. ONLY 27 ARE KNOWN TO US.
The "USIR" (United States Internal Revenue) watermark error occurred when a supply of paper reserved for revenue stamp production was used for printing the 6c and 8c postage stamps. Our updated census of this issue, published at http://www.siegelauctions.com/dynamic/census/271a/271a.pdf , records only 24 used copies certified as genuine by the Philatelic Foundation, plus three uncertified copies. Fourteen of those certified do not specify which letter is present. The other thirteen are split exactly equally between the "I" and "R" of the watermark. Many examples have perfs either close or touching the design.
Census No. 271a-CAN-07. With 1986 P.F. certificate