ok just curious - one of mine is like that as well - the other is the same as the OP base in this post and isn't signed but has been confirmed by Norman as his.
Is yours extremely heavy for size?
Chriss would you say yours was extremely heavy? I do think they look very similar but it's quite difficult to tell by photos alone. Sue the iridescence on the NSC pieces is something special I think. It's very high quality don't you think?
The only other places I can think of as sources for the bowl might be say Siddy Langley or someone who worked with her, or maybe Neo glass or Peter Layton (but my PL piece has a beautifully finished ground flat base). I also thought Siddy Langley pieces would be signed and I don't know about whether her bases would be finished like that. And I've never held a piece of Neo art glass so it would be difficult to know and I thought they always signed as well
On balance I think it is close to Sue's NS-C piece - it would require more investigation though