Abstract: A variable optical stencil assembly has a plurality of discs (1) each of which discs (1) is of substantially equal diameter and comprises a plurality of windows (3) therein, disposed around the periphery thereof and each having a respective character or combination of characters or a set of characters therein. Each disc is rotatably driven about a respective axis of rotation by drive means (2). The assembly comprises not less than three discs (1) and not more than five discs (1) and each disc (1) overlaps with the other discs (1) at a central point between the axes of rotation, such that a window from each disc (1) is aligned with a window from each of the other discs.