O comando a seguir é provavelmente o que você está procurando:
duplicity collection-status file:///backup-folder
exemplo:
Found primary backup chain with matching signature chain:
-------------------------
Chain start time: Mon Mar 4 10:37:27 2013
Chain end time: Fri Mar 15 15:42:22 2013
Number of contained backup sets: 3
Total number of contained volumes: 10
Type of backup set: Time: Num volumes:
Full Mon Mar 4 10:37:27 2013 8
Incremental Fri Mar 8 15:53:07 2013 1
Incremental Fri Mar 15 15:42:22 2013 1
-------------------------
No orphaned or incomplete backup sets found.