HELP! Cleaning out a cupboard today, I came across two vintage glass print plates (wrapped in a newspaper from 1977). They are about 6x6 flat pieces of glass that look somewhat like negatives. I scanned them in. I remember buying this particular one because it reminds me of my father's mother. Do any of you know the era of these glass plates? All the info I've found so far has to do with wooden or metal plates. I may have to call a local antique dealer. If any of you have any information, please let me know!