I've emailed this question to my father, who has been a terrific source for me for this kind of thing, but I figured I'd poll the hive mind here as well - you wonderful folks with long memories and knowledge of law enforcement might be able to help.

Here's the question: It's 1950. Someone from federal law enforcement (FBI or US Attorney's office in particular) wants to trawl through NYPD misdemeanor arrest records looking for dirt on a limited number of people - between a few dozen and a hundred. The charges need not have amounted to anything - the very fact of an arrest would be adequate for this person's purposes.

How might that search work? This is both a question about the physical storage of the records themselves, and what kind of access someone could be granted to them.

In my original imagining of it, I thought of someone in a dusty warehouse poring over carbon copies of arrest records. Would there have been such a central warehouse, or would the records be stored in the individual precinct? (That would be fine; perhaps even preferable, now that I think about it.) Would it be possible for someone with federal law enforcement creds to be given access to a general set of records to examine, or would they absolutely have to cough up the list of names and request records on those specific individuals?

I would prefer the anonymous trawling route, rather than a specific request -- even if it's not SOP, if it's at all possible that the fed guy could pull strings to obtain that kind of anonymous access, I can work with it.

For any thoughts or insights or informed speculations that you have -- thanks!