Here are two matching S&W Rainbows. Both have four images on GlassGallery, two views, through the base, and pontil finish. Click to enlarge each main image, click thumbnail to change image.
Egg shaped vase, h. 8Ľ" 21cm, maximum d. 7" 17.5cm, w. 3lb 14Ľoz 1776g, via http://glassgallery.yobunny.org.uk/displayimage.php?pos=-15317 Tall bucket shaped vase, height 9˝" 23.8cm, weight 3lb 15˝oz 1808g, via http://glassgallery.yobunny.org.uk/displayimage.php?pos=-20899 There may be a correlation between height and weight which is fairly constant for any one glassmaker, and could help attribute mystery examples. I think it unlikely to be linear (height to the power of 1) or cubic (height to the power of 3), but could be square (height to the power of 2) or a mixture of linear and square, where weight equals A times height2 plus B times height plus constant C.
If you would like to try this, please would you provide accurate height and weight for each of the examples shown. It doesn't matter whether you use imperial or metric or mix them — we can do any conversions. Use the system that you know best. Again, with fractions and decimals, use whatever you are happiest with.
Bernard C. 8)
ps — No.2 is the one I referred to earlier in this topic. I will be bringing it on Sunday should anyone wish to do a comparison.