Jerry:
I only know what Henry says on his website:
http://www.zeisscamera.com/ContaxIIa/Page4.html#Bump%20Removal
From: Jerry Lehrer <jerryleh@xxxxxxxxxxx>
Jan,
I wonder how Harry Scherer handles the infamous 'Zeiss Bumps", which
are caused by brass or steel rivets it the cast aluminium body, causing
bi-metallic corrosion. Rolleiflexes also suffered from that. I assumed
that neither Zeiss nor Rollei ever had metallurgists on their staff.
Jerry