Cody has the ledgers, and once you are a member getting a serial number lookup isn't that expensive. Quite a bit cheaper than it ever has been before. Even a $150 membership lets you buy a pack of 50 serial number lookups at $5/each for $250 total.
Even counting in the $150 membership, that's under $8/lookup - much cheaper than was possible ever since Roe had the records. You don't get a letter for each one, but you do get all the info. I'm waiting on my first set of info.
If you don't want 50, just want 5? The $150 membership gets you 5 searches as part of the membership, so that's $30/apiece. Not much more than Callahan was doing, and most of the $150 is tax deductible.
Want just 1? Well.. that's where it sucks. $75 letter for non-member.
Let me know if you want to start taking contributions as a sort of "group purchase." I'd be happy to chip in and I would have no problem with you or any other member of the forum becoming the holder of the membership on behalf of us all. A group effort like this could end up being a new way for the forum to get information from an established archive that otherwise would be speculative or piecemeal.