Abstract: A stack of image receiving sheets, wherein each image receiving sheet has on one side of a support an image receiving layer, includes a cover sheet protecting the image receiving layer of an outermost image receiving sheet. The cover sheet has a detection mark distinguishing it from the image receiving sheets.

Abstract: Thermal image recording apparatus which can be set for recording on any of a plurality of different types of recording sheets, e.g. opaque or transparent, and wherein a sheet is fed by a suitable sheet feeder, preferably a rotatably drive sheet feeding rollers, from a supply a cassette or other supply source to a printing head for recording thereon, has a sensor for detecting the type of recording sheet used for the recording and for generating a control signal which is effective in the event a given sheet sensed by said sensor is of a type different from the type for which the apparatus is set, to disable the sheet feeding rollers from further feeding of the sheet to the printing head. Preferably, in the event of a mis-match between the type of sheet being fed and the machine setting, the direction of the sheet feeder is reversed and the mis-matched sheet is returned to its supply cassette.