Okay, from the what I can tell John Archer did a single season of The Shadow (which logically, would be season 8). Steve Courtleigh (based of a single webpage I found) did 6 episode before deciding he couldn’t do the role. Those episodes were in season 8 (although the website I’m finding that on calls it 11, but I’m ignoring that ‘cause the rest of the info matches up). I’m going to guess it’s the last 6 episode of Season 8. Only 2 of which survive. (Only 4 episode of season 8 survive at all).
Which would fit with the other info of there only being two surviving John Archer episodes.
No. Because there would be 3 in the last 6, and only one other. And John Archer had 2. So maybe not the last 6? Maybe not 6 in order, just to fill in, since John Archer had trouble balancing his schedule? Did he miss some and Steve filled in?
I’m going to see if I can confirm this. Find other sources.