I'm the guy in the email exchange who guessed these to be by Joe Blackford, based on this blurb from the 1970 G&A Annual.



I recently saw a similar pair on another site.

--- An addition for posterity: Similar grips - finger grooves, same checkering pattern, same upper profile - are shown in the R.L. Wilson Colt Book of Colt Firearms on the personal Official Police revolver of Al Goodwin. Sadly, the maker is not named.