in view of your comment re thickness, you may not get much of a ring if this piece is 'flicked' - apologies if my comment was misleading - I was making reference to the ding and lead content more as a general comment applying to quality glass. We all know about the long ring produced when flicking high quality drinking glasses, with a lead content. You can try tapping with a wooden spoon and you may well produce sufficient of the right noise to determine that yours has a lead content. Most decent sized lumps of cut glass (especially vases) have a reasonable lead content, partly because cut lead glass disperses/reflects light much better than non-lead glass, but also because, apparently, glass with a lead content is easier to cut.
If something looks ordinary to you, you can bet it's going to look ordinary to everyone else - thus no real value - try to go for pieces with a makers backstamp - it gives instant provenance.

As we've said, Stuart pieces that can be attributed to a particular designer or design name, are vastly fewer than the shed loads of ordinary mitre cut material, and if you can get your hands of Hajdamach's C20 book, you will see a great difference between the ordinary and the special. The other benefit of having, for example, the Hajdamach book, is that you can learn to recognize the special pieces - which do, believe it or not, turn up occasionally on ebay, and can sometimes remain unrecognized by the masses. The same applies to the better cut pieces produced by Thomas Webb and Webb Corbett. You just have to hope that Mr. B is also not looking at the same time as you.

do try and get the Hajdamach book, it really is good value for money, even if too bothery heavy.
P.S. apologies that this is rather long winded.