I spotted this photo at My links page Northern California Bus Fans to the right of Your computer screen.

This photo is entitled "The CTA in 1952".

During the year of 1952, the recently formed Chicago Transit Authority wich began operations in May of 1947, had purchased The Chicago Motor Coach Company. The 1940's era old look General Motors TDH series transit bus that is viewed here, is wearing the "New" CTA logo on the sides of the bus, but the roof still has "The Boulevard Route" slogan lettering from the recently purchased Chicago Motor Coach Company.

Many of the former Chicago Motor Coach GM buses acquired by the CTA in 1952, worked in daily transit service until they were eventually retired between 1970 and 1972. Some went on to become maintenance work service buses after retirement.