Is the following manuscript publically available?
Dana Scott, 1969, A theory of computable functions of higher type. Unpublished seminar notes, 7 pages, University of Oxford.
There is a discussion of this paper in section 8.1.2, Types as sets, in Cardone & Hindley, 2006 History of Lambda-calculus and Combinatory Logic; additionally section 10.1, Domain theory, traces back to this manuscript some crucial order-theoretic insights.