Ming, would you mind taking a look at this thread I posted a little while ago, if you haven't already done so?
http://www.glassmessages.com/index.php/topic,23519.0.htmlIt's about an engraved stem I got recently, and I'm very keen to know more about it.
I was also curious about what you said about color. Do you mean that late 19th C glass is substantially different in color from early 20th C glass, and if so, do you know why? I was just writing someone an email today, wondering whether sun may have turned some ABP greyish. Sun-purpled glass sometimes looks grey before it gets purple, and I thought perhaps something about the formulas allowed it to get grey but not actually turn purple.
Comparisons with modern glass aren't always very helpful. My modern, everyday glass is greyish, too.