How do you document your record collection for insurance/theft/fire?

Photographs/videos of the collection sure helps, lists/spreadsheets too, receipts if you have them, and if you have any particularly valuable records, you might even want to obtain an appraisal so there’s less opportunity to dispute an item’s condition. Be sure to update them periodically, and also make sure these things are kept in a separate location from the records – would really suck to lose both the collection and records establishing its value from the same event.

And keep in mind that if the collection is valuable, a standard homeowner’s policy or renter’s policy is likely insufficient to cover the whole thing without a special endorsement. Things like record collections may be subject to a sub limit.