A media sheet which can be a label sheet assembly is provided with bar code information thereon defining the layout of the labels on the backing sheet, and/or a validation symbol or mark. A sheet feeding mechanism which may be part of a label peeler has at least one sensor which reads the encoded information and/or the validation symbol, and either takes an action with respect to the sheet, does not take the action, or takes a different action with respect to the sheet depending on the encoding or symbol on the sheet. The actions can include advancing the label sheet according to the layout of labels on the sheet, dispensing labels depending on the presence of a validation code, or other actions.