From a press release I received today:
On Saturday, August 22 at 12:00 p.m. ET, MLB Network will air a new episode of All-Time Games with the July 12, 1969 matchup between the Chicago Cubs and the Philadelphia Phillies at Wrigley Field. The game features Hall of Fame pitcher Ferguson Jenkins against Phillies All-Star Rick Wise as Chicago looked to gain on the New York Mets in the N.L. Eastern Division. The game also includes Hall of Famers Ernie Banks and Billy Williams as well as ten MLB All-Stars including Don Money and Ron Santo.
I have seen this game before -- in fact, I own a copy of it. It is the earliest surviving complete regular season game telecast; not the WGN telecast, it was the NBC Game of the Week, a Saturday at Wrigley Field. You can buy it yourself from a company called Rare Sportsfilms which is headquartered in Naperville and deals with all kinds of old sports events, game telecasts, films, etc. (No, they didn't pay me anything for the plug -- I just think they have a cool product.)