6 d. greenish grey, 2 single copies with clear to mostly large margins, tied by numeral "5" to envelope (slightly reduced at right) with adjacent clear "BRENTFORD MY 19 59" and "PENSION OFFICE MAY 23 1859" to the controler of pensions in Washington D.C.; an attractive and rare double-rate letter, according to Wilkinson only 4 covers at this rate bearing 6 d. on wove paper Provenance: Dale-Lichtenstein (1969), 'Consort' (1977, with RPS certificate), 'Foxbridge', W.E. Lea, Wilkinson (2007), Joseph Hackmey (2011)