They probably came from a Duplicati update around Nov 29 (did you update to 2.0.4.5 beta then?) which caused an update of the database format and left you backup copies of the old one in case it was useful.
Any progress in new beta?
Downgrading / reverting to a lower version
If this was your scenario, and you’re sure you don’t want to downgrade (or wish to take your chances with downgrade by manual database manipulation), then possibly the safest path is to move these elsewhere, ultimately deleting them after routine backups on Duplicati update seem OK and you opt to move forward.