There is a article on Allan Jefferies, written by his son Nick, in The Classic Motor Cycle, October 1994. It mentions the Argentina venture….
“As Scott only paid spasmodically he went off to ride speedway. However, his main job was working as a mechanic for Frank Varey at the Belle View track in Manchester.
He went out to Argentina late in 1930 as a reserve rider and Varley’s mechanic. And in later years my father used to travel to South America to look after the American speedway ace Sprouts Elder. In 1930 they rode Scotts, and tried to interest the local police in buying some. A standard model accompanied them for demonstration purposes, but they substituted Varley’s speedway engine before the test took place. The police were most impressed and ordered 50 machines”.
Allan Jefferies died in 1978, but his sons Nick and Tony were TT winners in the 70’s, and are probably still about.
