Roberto asked in 2005: the John Sinclair noted by Otto Andersson in 1938 and the John Sinclair recorded on Peter Kennedy's anthology Sailormen & Servingmaids (I think in 1961) are the same person?

The booklet of the Caedmon/Topic album "Sailormen and Servingmaids" noted:
A brief version of it appears as no. 113 in Child without a tune, but this is no match for the variant which old John Sinclair of Flotta in the Orkney Isles turned up with in January 1934. He has since been visited by Swedish folklorists [i.e. Otto Anderson] and recorded for the BBC. [which I assume is the version on "Sailormen and Servingmaids"]