A pen tool for use with a machine vision interactive input system comprises an elongate body and a tip arrangement at one end of the body, an end surface of the body at least partially about the tip arrangement carrying light reflective material that is visible to at least one imaging assembly of the interactive input system when the pen tool is angled. Since a markup document can be displayed in a reproducing apparatus having a viewer version lower than a specification version of an authoring tool used to author the markup document. A second coating without a UV indicator is applied over the first coating and visually inspected, with the first coating being visible with a UV light at portions wherein the second coating does not cover the first coating.