At my previous bank we obtained conductor info on cash transactions of $5,000 or more; this was in place for quite a few years. At my current bank (which is much, much smaller) we stick with the $10,000 threshold.
When asked about the need for the ID, our tellers usually stated that it was bank policy (at the previous bank). Here we offer the pamphlet.
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My opinions do not necessarily reflect those of my employer.