Thanks, Cat and Paul.
Yes Paul, the silver base is rather tasty, isn't it? Quite heavy, too.
Cat, that was useful information about the pontil. I hadn't realised they were sometimes polished smooth, but I suppose it should be obvious. However, based on one source I found, that now starts to steer me away from thinking this is Fenton. This is a good thing; I had this feeling Fenton might be more modern than I want to concentrate on.
Any other advice and suggestions will be most welcome. I thought you might also be interested in the colours I get under UV.
Thanks again.