Design inspired from a wooden tool Vaughan Smith fashioned to smooth rims when finishing a thrown pot. You can use ¼" rubber bands that at one time came with bags of clay or you can buy them. Other option is to cut a strip of chamois leather and fashion it around the finisher. Muddy picture shows chamois cut around 5/8". This is a clip of Vaughan using the DDD model @ 7:04 in video:
The author hasn't provided the model origin yet.