Hi Ian
There is a photo of a Bristol Scout C of the RNAS (possibly 3034 at Redcar) that is stated in the caption to be fitted with containers for Ranken Darts, two containers visible under the fuselage beneath pilot’s cockpit. This is photo 34 on page 14 of Jack Bruce’s ‘Bristol Scouts’ Windsock Datafile 44, if that is of any use.
Mike