Sheldon Brown sez: "...Be aware that given enough time the leather strap and whatever dirt finds it's way underneath will mar the chrome plating on a steel hub. (i.e. Sturmey-Archer).."
... I only used them on dull-finish unanodized alloy hubs back when I used to make/use them (cutting up an old leather belt). They really shine up an alloy hub barrel nicely.
Peter
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Peter Brueggeman
San Diego California USA
pbrueggeman(AT)ucsd.edu