Hi Chris,
My final random thought on this, which is probably of no help at all but as I've been spending weeks and weeks trying to sort out a whole batch of paperweights I have, I notice some similarities to Merlin glass weights I've found and remembered that Liskeard used to make weights for St Tudy and sign them S T so could this be a later incarnation of the same principle - do/did Merlin make weights for others?