Could it be for picking those double sided pin tumbler locks that they were discussing in this forum? I don't really know, but it kind of looks like it would work for that.
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that is a very old design, you may see it in things like articles about houdini, I have also heard it refered to as a mailbox pick, presumably for ones private box when the key is lost, I never quite figured out what sort of antique locks it was good for.