I found in my collection of stuff an article by Werner Baus in DAS
MECHANISCHE MUSIKINSTRUNMENT, June 1980 all about Popper metal unit
valves. I ran it through a German-to-English translator program I have
and it's understandable in a disjointed sort of way. If anyone is
curious, I can describe how he restores these curious valves.

    I could not determine what glue is used on the pouch (which is
glued to aluminum). Do any of our German readers know?

Philip Jamison West Chester, PA USA