Stack of image receiving sheets with detection mark

A combination of a processing apparatus, having a sensing means and a control means, and a package including a dye donor element comprising on a support a dye layer containing a thermally transferable dye and a stack of image receiving sheets for use with said dye donor element wherein each of said image receiving sheets comprises on one side of a support an image receiving layer comprising a dye-able resin, and wherein said stack includes a cover sheet protecting the image receiving layer of an outermost image receiving sheet, said cover sheet further comprising a detection mark located at the center of said cover sheet for distinguishing it from said image receiving sheets, the presence of said detection mark being detectable by said sensing means, and converted by said control means into an indication to said processing apparatus that said stack is correctly positioned.