A disk-shaped gauge of molded plastic has raised hubs at both sides with a surrounding disk providing support faces around the hubs. The hubs have successive chord lines at equal intervals which are serrated to form linear gauge edges, the number of serrations per 20 mm length of the gauge edges being graduated from 8 to 16 and fractions thereof as are marked on the hubs. Stamps placed on the support faces are checked for mating engagement with the gauge edges to determine the gauge of the serrations of the stamps.The classification of stamps by philaterists require the determination of the numbers of serrations along the edges per a 20 mm unit length since this is important in ascertaining the value and character of the stamps.