Dear Ric and Chad, fantastic. Thank you for the rapid response on this. Pretty excited about my first handmade German marble! I include a close-up for confirmation. Thank you Chad for showing this nice selection of sulphides. I add a couple more images, as for marble 1526 it reminded me of an "end of day" marble, it seems to be made of a lot of small pieces of glass. Some of the other glass marbles are irregular and with a single small "detachment point" (eg marble 1528) is this an indication for "older" or not necessarily? The last one (1529) reminded me of a "clambroth marble, but the ornamentations run in the wrong direction. Thank you all for sharing your expertise and opinions. Have a great day.