25c blue 'Hidalgo' postal stationery envelope with watermark (UPSS #E9, H&G B9b) with '1978' number and 'QUERETARO' district opt at top left used in December 1878 with good strike of small oval FRANCO EN CELAYA cancel. Addressed to GUANAJUATO with small handstruck '23 DIC 1878' date marking in blue on reverse and manuscript arrival endorsement on front dated DIC 24/78'. Part of backflap missing. A rare and likely earliest known use of the watermarked issue which is recorded as being issued in 1879.