One of the intriguing aspects of this toy is that it is clearly an American model, but it is stamped with ‘Made in England’ and ended in a London’s Hospital.
Some clues from other internet sources provide some context – for example, another bottom print from a 1939 model Tootsietoy model identify the manufacture as Lesney [1] - the manufactures of Matchbox cars [2]. Other sources are suggesting, as expected, that some models were made in the USA (for example, the Tootsietoy page on Wikipedia). Another detail is that some Tootsietoy models from 1934 where created by Hornby, another famous English toy car manufacture.
According to booklet Dinky Toys [3] Hornby started operation in 1931 and the Dinky Toys brand was created in 1934. According to this booklet the process of creating die cast cars was imported from Tootsietoy, with British manufacturers quickly excelling in the production of these products, so this might explain the connection. In addition, the booklet notes that in the late 1950s, Dinky Toys were looking for opportunities in the US, as it was more prosperous and bigger market.
So interestingly, despite the external competition between these manufacturers, there was some level of co-operation and information sharing between them. The model that is at the centre of the investigation was and the ongoing connection with Dinky Toys means that it was likely produced by them. So now to the interesting questions – with Tootsietoy in Chicago and Dinky Toys in Liverpool, how did the requests for production and the model description and sketches travelled? Surely the people who worked in Liverpool haven’t seen many Ford Sunliners. What were the reasons to pass the manufacturing to Britain? Did engineers travelled between the two factories and what sort of knowledge was shared or not?

[1] http://cgi.ebay.com/Rare-Tootsie-Toys-die-cast-vehicles_W0QQitemZ2604247...
[2] http://en.wikipedia.org/wiki/Lesney_Products
[2] http://www.tsrfcars.com/toys-tootsietoys.htm
[3] David Cooke, 1999, Dinky toys