hi - Christine is far more knowledgeable on these things than me, so appreciate the reply Christine. Sorry to be thick sendhandfran, but I take it you're saying your dish is uranium - would appear both of your pix have been taken in daylight, and not using a u.v. torch.
Often, when exposed to morning sunshine, the short wave length light rays will make the uranium react quite strongly - gives a nice glow on the edges.
My rather uneducated guess is that your dish is not sufficiently 'amber' to be T/Webb's Sunshine Amber from their Gay Glass range - but no doubt Christine will put us right.
Easy to tell if you have a grapefruit dish, as opposed to a general purpose desert dish - the base has turned up outer edges which provide somewhere safe to put your pips - saves spitting them out.

I'm sure that sundaes are always tall and cone shaped, but perhaps I'm wrong.
P.S. If you look at the Board's archive section 'Library of Thomas Webb Colours', am sure you'll find plenty of examples of T.W. material with which you can at least compare colours.
I could be wrong, but have an idea that Walsh pieces relating to this shape and colour have an iridescent finish, so will have a different type of surface appearance.