1 1/2 inch scale Marshall semi-portable engine

A well-advanced Marshall semi-portable, based on the 1 1/2 inch scale portable design by A.J.Avery, "Manufacturing Model Engineer" of Brighton, in 1940 and complete with three sheets of blueprints.

Although built to the same scale as the Hughes/Kibbey portable design published nearly 40 years later in "Model Engineer" magazine, it's a significantly large engine, presumably based on one of Marshall's larger designs.