I do love a good mystery. Glassbottlemarks.com is an amazing research tool that I use often and and it is wonderful that you know someone there that can help so quickly. Another resource I sometimes use is https://sha.org/bottle/index.htm (I am not sure if the 2 sites are related or not).
I found this site recently when I was researching milk bottle before listing them in my Etsy shop. Perhaps it will be of use to you too? https://milkbottle.collectionhero.com