ETA. I didn't know Giampaulo had solved the mystery. I replied to Nev...
Thank-you so much Giampaulo, and welcome.
![Wink ;)](http://www.glassmessages.com/Smileys/classic/wink.gif)
I was just looking at the mark - the glass itself rather distracted me and I thought Schriever could be it, when peering from a squintish angle just now.
I'm sure there are loads of German names of folk now resident in the States and elsewhere.
Something as good as this should be attributable.