The Sycamore was indeed used during the disaster reliëf in 1962 Flooding.
Wangerooge photos
I could not identify the 1920s plane 100%
I thought Rumpler C VII because of the N shaped struts, No spinner cap and General layout of engine exhaust and radiator.
Only the cutout in the upper wing for pilot looks to be wider than on Rumpler photos.
The Aviatik comes also close, has a wider cutout, but also a spinner cap.
Anyone who can give**a Final word on it is welcome.
*