And I have two questions about the way it's calculating. Are the current values manually entered or from some sort of feed?
They're computed from auction data.
When a MISB price is missing, does it fall back to MSRP?
No, but I've been meaning to do that for years. I've put in a lot of work on the appraisal system, but even now it's still a little half-baked. I need to modify it to default to "price paid" values from collection data when no auction data is found (and to MSRP when that fails), improve the price history presentation, on and on. I'll get to it, hang in there.