Very interesting. When I was a kid growing up, we had a copy of The Mercury’s 100th anniversary souvenir from 1954 that had been left behind at our place from the previous owners. It included some ads for both 7HO and 7HT at the time including some of the old program lineups. And I’m kicking myself I never kept that magazine. I think my parents threw it out in a spot of spring cleaning
But I did find this recently, this promo card showing 7HO’s ratings back in 1987: