At a recent gun show I saw a pistol the owner fondly believes is a Devel. It looks sorta like the 'Basic' Devel, but unfrotunately I can't remember the details. However it was built on an Illinois State Police pistol: complete with ISP markings and the extractor that many of them had. Did Charles Kelsey modify customers' guns, or did he just work on new S&Ws?

He worked on customer supplied guns....

yes, he did as well as make his custom own pieces. He was extremely talented and his guns sell for BIG money today. A testament to his work.