A rare US postage stamp from 1868 has sold for more than $1m at an auction in New York city. The three-cent, rose-coloured "B Grill" stamp was sold in a three-day Siegel auction galleries sale that ended on Thursday. The auction house said that only three other known examples of the stamp remain. "B Grill" refers to the embossed pattern in the stamp paper. An anonymous buyer put in the winning bid of $1,035,000 (£620,000). The auction also included one of the most famous stamps, the so-called "Inverted Jenny" from 1918, which features a biplane accidentally printed upside-down.