the moulds apparently were made to include the Reg. No. within an oblong box, and it's this Rd. No. 20086, from 8th Jan. 1885 that appears - usually - on these swans. In Ray Slack's book, he gives a height of 2.5 inches and length of 3 inches, for both an opalescent example and one of the black ones that were destined for the Oz market. Always possible there were other moulds that didn't carry the Reg. No., and there may have been other sizes of swan too, from B. & T., and just to confuse matters there are many swans out there that probably had nothing to do with B. & T. Apparently designed as a posy vase rather than a salt, which is how some sellers promote them. How it can be shown that a swan without the Rd. No. is unquestionably B. & T. I'm not sure.