1c Green, Rotary Perf 11 x 10, Vertical Pair, Imperforate Horizontally (538a). Mint N.H. block containing two pairs, bright color, exceptionally well-centered, Extremely Fine Gem, a superb block, ex Whitman, with 1997 P.F. and 2009 P.S.E. certificates (Superb 98; unpriced in SMQ)