Thanks Drwatson for your help. I had the inkling that it may have been Canadian. I am a bit of a Hubcap collector and this one had me completely stumped.
The attached picture are the DeSoto Hubcaps in my collection. I have since purchased a 1960-1961 DeSoto Hubcap, not pictured.
I think that my DeSoto collection is now complete, except I don't have the rare DeSoto Adventurer hubcaps and am not likely to either.
I mark the years on the reverse side for identification. In 1958 and 1959, Chrysler Australia imported DeSoto Firesweeps, so all the others have been purchase from the USA.
The earlier DeSotos (and Dodges) sold in Australia up to 1956 were all based on the Plymouth, with the 1955 and 1956 models retaining the same body as the 1954 models with slight changes.
Not a cheap hobby with our poor exchange rate and the high cost of postage. I hope that you enjoy the attached pictures.