Hello,
Currently on ebay is a photo of USN Curtiss R-6 A-197 at:
https://www.ebay.com/itm/N808-C-1940...oAAOSwGTBe8PdS
Another R-6 can be seen here alas no serial to be seen:
https://www.ebay.com/itm/USN-R-6-Nav...IAAOSwMwhe8OBS
Edit
Quite a day for Navy Curtiss photos. Also on ebay is a photo stated to be original of the Curtiss Model E AX-1 at:
https://www.ebay.com/itm/USN-1st-Air...kAAOSwy81e8M9v
Regards,
Clint