I just read an old article by Jack Lott and the first rifle was a rechambered CZ 458.

The second was a rifle he built for a Swissair pilot. A left hand Remington 700! (Egads, don't let your children read this)

The third, I think, was the Ruger. He appearantly did the metal work and Hoenig handled the stocking.

He was kinda vague about the timeline except to say the Remington was done in 1977.

Previously he had developed the 460 G&A and a shorter 404 based 458 in the early '70's.