No, I did the entire table. That helped me find corner cases and errors in my logic having such a bigger range of source data.

Maybe I don't fully comprehend what you're saying... but is it even possible to do this?

I mean what if at some point particular entries were manually tweaked and the database was updated to fix an error in an invoice or something. And then you recreated data from what you assume is 100% reliable data.

I'm happy to try to understand if you don't mind simplifying the explanation.

I can't remember the specific details now (almost 20 years have passed!), but the STKM table was effectively a performance/convenience data store. Every bit of information was available from other transactional data, but in order to actually have a chronological historical view of "stock movements", it was maintained in this central table.

Probably compared their code's recreated table against the table from the day old backup.

If twenty years worth of data (up until two days ago) match, then the recreation of the missing day is probably fine too. It's not guaranteed of course, but...

Wow,

I'd still not touch previous data.

I'd use it just for ensuring correctness, but I'd not touch it

Where did you get the 20 year old data from in that case? Actual paper in drawers, a directory of all invoices on disk, or some other database?