I've never been able to find ANY proper mention of this, but I found it this evening. So, now I have a date, although another listing on the same site has a second date - I suspect maybe a rerun?
June 8, 1972 episode 171
Merv's guests are actor William Holden talks about his African Conservation Ranch, producer Martin Rackin explains how he began a career of reporting with the New York Daily News, comedian Dom DeLuise discusses his latest film "Every Crook and Nanny", singer-dancer Lola Falana, comic Chip Hand, actor-writer-director-composer Bruce Kimmel and Valerie Gillet.
Now, someone find me this damn thing, seriously.