I only saw one mention of the early Shimano side pulls. If memory serves correctly in the early 70's Shimano basicly copied the Campy record side pulls for less than 2/3 the Campy price. These were nice brakes and almost as attractive as the Campy's. I am still riding an old bike with these same brakes. I believe that these were the first high quality brakes that Shimano produced.
I had a bike built with each back in the 70s... the Campagnolo brakes cost $113., the DuraAce $68.