ah,I don't perceive that as the same blue as the lamp

It's lighter. I know it's all perception and lighting and batch mixes etc, but I still think it's slightly different.
However ... it could be that a Burtles and Tate link is worth searching for.
Again this is probably a ridiculous question but is it worth looking at who registered metal work designs on the date on the lozenge? or is that an enormous job? It could just be that a glassmaker will be found amongst those registrations.
Apologies if you've already done this.
m