Thank you for your input. I think getting to the bottom of the dating is important and the labels are key to that. My guess is the "Avventurina V. Nason & C Murano, Italy" label is the oldest and so far I have only found this label on the Black/Aventurine and Black/Red/Aventurine lines. (By the way, it is spelled Avventurina. The label in the Murano label library is missing the upper right corner.) In each of those lines I have an example of one or two models not yet found in the other colors. In answer to your question, most of the models of the Black/Aventurine line can be found exactly duplicated in the color lines. The small 3 inch round ashtray was produced in all 6 lines and is one of my favorite displays.
I found one example of a "V. Nason & C Murano, Italy" label on the Black/Aventurine line. As far as I can tell this label is not in the library.
Then there are the labels from "Weil". My research produced the following on this company; "Weil Ceramics & Glass, of Fifth Ave. NY, were importers of high quality glass in the 1930's until the 1960's. They were taken over by Lladro in 1973". I have found two variations of the Weil label; "Weil Ceramics and Glass" and "Venetian Weil Murano - Italy". I have found these labels on the Black/Turquoise/Aventurine and Black/Yellow/Aventurine lines.
Then I have a label on the Turquoise/Aventurine line that I may try a black light on. It is very badly faded but from what I can tell it is not in the label library.
Of other interest is that most but not all of the models have the raised letters ITALY on the bottom. Would the lack of "Italy" be an indication of a non export item?