This is quite interesting! A 1955 "pseudo" stereophonic simulcast of NBC/The Bell Telephone Hour's adaptation of "A #ChristmasCarol," synced via NBC's #WMAQ (then-WNBQ) Channel 5 & AM 670 in #Chicago!
Wonder if NBC-owned WRC Channel 4 & then-AM 980 in Washington, D.C. did something similar?