India has a long and varied postal history and has produced a large number of postage stamps. These have been produced by a variety of techniques including line engraving, typography, lithography, photogravure and . Stamps have been produced both for postage and for service or revenue. Definitives and commemoratives have been issued. Stamps have been produced both as unperforated sheets, perforated and miniature sheets. The stamps have been produced in a number of shapes - the Scinde Dawk being rounded and some, like the stamp on the Bombay Sappers being triangular. Recently the 2009 stamp on Louis Braille had braille imprinting on it in addition. Many cases of overprinting exist - for converting the use of domestic postage stamps to service; to earmark stamps sold by field post offices at