There are many "barbarous radiate" copies of Tetricus types. They range in size from the sizes of the originals (say, 18 mm or so) down to far smaller. 9 mm is about as small as you will commonly see, but I have one of 6 mm with a tiny reverse type. I have heard of smaller diameter examples, although not with clear types. You can see some on this page of barbarous radiates: http://augustusmath.hypermart.net/BarbarousRadiates.html