Thanks Christine - I didn't have a clue what that meant to be honest

I was a little confused by it. They also said it seems to have been made pre-1930 - I think it possibly dates a good 40 years earlier than that.
I've just started trying to read up on it the gilt enamel on sodium glass

For comparison, this jug on this link has an insect on and was confirmed as Moser by them
http://www.glassmessages.com/index.php/topic,20769.msg117487.html#msg117487Sue thanks

and thank you for checking those out, that's really helpful to be reassured about the quality. Yes the 'incalmo' neck bit - it's a little strange in that it isn't entirely smooth like you might find with say a funky modern incalmo cylinder type vase , you can feel an indent on both the inside and the outside right round the ring where the blue has been sat on top of the clear glass - I can't think that was easy to do. The piece is huge as well, so it's amazing it survived the annealing process isn't it? or is it?
The more I think about all the bits that went into making this jug, the more I think it must have been vastly expensive to produce.
OH maintains it speaks French to him. And it does have that look, it's terribly 'pretty'. But I'm still favouring Bohemian and probably Harrach for various reasons at the mo. I wondered about Muhlhaus for the enamelling - I think I found something on here - I'll try and find it again to link it.
Thanks

m