Scarce is a good word for these early Evans-Colson bikes. I see nothing amiss in his story regarding the history. The company bought out Colson in 1953 and released their first models for 1954, in Plymouth Michigan. I'd agree that this is a '55. They employed Harley Earle on the design of the bicycles. This early Evansaction springer was only used for a brief time; 2 years or so.
The spot in question on the top tube looks like a recent paint chip, maybe? It's reflective like bare metal. Otherwise, condition is quite primo. I think it'll command pretty good money; they don't come up often.