Washington and Washington. Both the stamp and the stamped envelope depict Washington. The envelope is Die 57 from the 1874 Plimpton contract. Scott number for the envelope is U163 which has 4 different possible watermarks and 5 different possible sizes. Impossible to determine size and watermark from the scan.
Perhaps a stamp expert will weigh in on the 3c Washington stamp which probably paid the additional postage for a double weight letter.