Last post, I made a protracted and over-detailed claim that basically, builders were stealing ideas from each other left and right in the 1960s. Here's a simpler argument for the same idea: look at just one recurring decorative element, and see how many different builders you can find who used it.
I've chosen the horizontal band of stone, set in a brick wall. There's no reason to think this particular element is inherently obvious or necessary; you can look at other buildings in the photos and see a dozen other ways to use field stone, and I can make up plenty more out of my head.
5223 N. East River Road - Redelco Corporation
6173-75 Northwest Highway - Losacco and Springston Builders
6847-49 and 6853-55 Olmsted - Guiffre Brothers
7418 N. Harlem Avenue - Parisi Brothers Construction Co. Inc.
7610 and 7614 W. Belmont Avenue - Nick S. Theodorau, architect. No word on the builder.