Hello,
Currently on ebay are two interestingly marked Rumpler C.I possibly of Kampfstaffel S 1 or Kampfstaffel 31 :
Rumpler C.I C.1864/15
ttps://www.ebay.de/itm/J286-Doppeldecker-Flugzeug-1916-Kennung-C-1864-airplane-Balkenkreuz-SCHLASTA/224310161890?hash=item3439ed71e2:g:SI0AAOSwhfZf-XNy
Rumpler C.I C.1865/15
https://www.ebay.de/itm/J285-Doppeld...IAAOSwyW9f-XMS
Regards,
Clint