Each time you save changes to an item, the version before is kept. On the item's page choose More → Edit history….
The list shows each earlier version, newest first, and what differs from now. Choose Restore this version to bring one back. Restoring is itself an edit, so it can be undone the same way.
Other histories are kept too:
- Holding history on the item's page — purchases, sales, splits and count fixes.
- Value history — every value recorded, including voided ones. See Correcting a mistaken value.
- Where it is — handoffs and returns. See Loans, repairs and consignments.
- Care & service. See Care, service and warranties.