If you don’t set Scrivener to automatically zip your backup, and use timestamp, opening the backup project adds the timestamp to the project’s name. Backup that and reopen it a few times…
You’ll end up with:
ProjectName-bak-Timestamp-bak-Timestamp-bak-Timestamp-bak-Timestamp-bak-Timestamp.scrivx
Having Scrivener to automatically zip the timestamped backup adds an extra layer of folder (which gets the timestamp) that prevents this.