I find these little Am Insulator pieces fascinating. As far as I know this picture represents the three dome types known and the basic colors available. No info is available on why there is different dome embossings. It is now a known fact that CD 105s where manufactured at the Lyndeboro(LYNDEBOROUGH) Glass House in NH. If you have any ideas on the dome variants please drop me a line. Also note that all three have different wire ridge configurations.