In two Los Angeles scenes in a glass elevator, a logo for consulting company KPMG is clearly visible on a building in the background, in the center of the frame. KPMG was created in 1987, when KMG merged with Peat Marwick. The building, now called KPMG Tower, was constructed in 1983.
While Bobby Riggs is watching television in the Rolls-Royce, he passes channels showing The Mary Tyler Moore Show and Kojak. Both shows were on CBS, but on different days, and neither was in syndication in 1973.
The images on the monitors in the TV production truck just before and during the final match are clearly simulated. Images shown on professional broadcast monitors of that era either had rounded corners with no gray areas around image, or rectangular corners surrounded by gray areas, but never rounded corners surrounded by gray.