There were three size variants; a small 4 inch size (10 cm); a medium 6 inch size (15 cm); and a large 9 inch size (22 cm). The suffixes used to denote these sizes were initially S - M - L with 'M' denoting Medium size not its usual meaning of applied decoration. On some examples 'M' is expanded to 'Med'. Later, the size suffixes changed to inch numbers.
Collection; Stuart Lawson
Medium size; height 15 - 16 cm.
Large size; height 20 - 22 cm.
Here the 'M' denotes applied decoration which is its more usual meaning.