Thank you for your considered reply Alan,
I'm not really entirely sure it's a 19th century one. I've had a number of the Bigaglia weights, both good and bad and the canes, colour, weight and metal are different. The surface of the glass is different, too; almost waxy and the canes are set quite deep within the glass. Also, the blowing rod used appears to be of a different size to the ones found on 19th century examples.
The colour palette is also different to the 19th century ones. The base colour is a quite distinct sea green, full of tiny pinhead sized "starfield" bubbles you often find in pre 18th century venetian and facon de venise cristallo. The only reference I've found to a millefiori weight that has a similar base colour was one fished out of a Venetian lagoon and dated to the end of the 15th century ( in the "minature di vetro" book, page 13 illustration 31- I'll try and post a photo of the illustration in the next couple of days).
Have you, or any board members ever seen a pre 18th century venetian weight? or know of specific references to the same?
Once again many thanks, in advance for any replies.