For future reference, here's a thread showing a steel etching plate:
http://www.glassmessages.com/index.php/topic,4637.0.htmlCoincidentally, I have another Rodefer Gleason plate purchased from the same seller (a member of the GMB). Nice bit of glass history. Maybe I'll add a photo of it to the "Decoration" section of the gallery, unless Ian would rather add his.