He spent four years apprenticing with Arnold Dolmetsch in England, returning in 1930, when he set himself up building instruments in a two-story space above a dress shop in Ypsilanti.
As he was the son of a jeweler, it was to be expected that Challis might include metal work in his instruments, and handmade brass hinges were a signature detail.
By the late 1950s his instruments still looked traditional from the outside, but were quite radical within: the frame and wrestplank were aluminum; bridges were brass; only the outer case was wood.
Of his soundboard construction, Mr. Challis said, "This is my only secret"; Wolfgang Zuckermann (in his 1969 book The Modern Harpsichord) conjectured that they were anodized aluminum.
[1] Website postings by several harpsichord experts independently report that Challis' soundboards were not single aluminum sheets but are honeycombed.